Solving Complex Pediatric Hip Cases: Valgusflexion Femoral Osteotomy

Patient Presentation & History

A 10-year-old male presented to the pediatric orthopedic trauma clinic with a progressive right-sided limp and insidious onset of chronic right hip pain over the preceding 18 months. The pain was primarily localized to the groin and anterior thigh, exacerbated by activity, particularly running and sports, and relieved by rest. He reported difficulty with activities requiring internal rotation and abduction, such as crossing his legs or sitting cross-legged. There was no history of acute trauma.

His past medical history was significant for Legg-Calvé-Perthes disease (LCPD) affecting the right hip, diagnosed at the age of 6. At that time, he was classified as Herring Lateral Pillar B/C border and Catterall Group IV, indicating significant involvement of the femoral head. Initial management involved conservative treatment with an abduction brace for 18 months, followed by close observation. Despite conservative efforts, the family reported a gradual decline in his functional status and increasing pain over the last two years, corresponding to the reossification and healing phases of LCPD.

He denied any systemic symptoms such as fever, night sweats, or weight loss. Family history was non-contributory. He was otherwise healthy, with no known allergies or previous surgical interventions.

Clinical Examination

General

• Antalgic gait with a noticeable right-sided abductor lurch (Trendelenburg gait).
• Appeared comfortable at rest but demonstrated guarding upon movement of the right hip.
• No obvious constitutional signs of illness.

Inspection

• Standing: Mild pelvic obliquity with the right hemipelvis appearing slightly lower than the left. Apparent shortening of the right lower extremity.
• Supine: Minimal true limb length discrepancy (LLD) of approximately 0.5 cm (right shorter than left), but significant apparent LLD.
• Muscle atrophy: Subtle atrophy of the right gluteal and quadriceps musculature compared to the left.
• No skin changes, swelling, or obvious deformities of the hip joint itself. Previous abduction brace did not leave residual skin issues.

Palpation

• Tenderness to deep palpation over the anterior hip capsule and in the groin crease.
• No specific tenderness over the greater trochanter or iliac crest.
• No palpable masses or effusions.
• Hip musculature felt symmetric in tone, despite subtle atrophy on inspection.

Range of Motion (ROM)

• Right Hip:
  • Flexion: 100° (versus 120° left). End-range flexion elicited groin pain.
  • Extension: 5° flexion contracture (positive Thomas test) (versus 0° left).
  • Abduction: 20° (versus 45° left). Painful at end-range.
  • Adduction: 20° (versus 25° left).
  • Internal Rotation (IR) in extension: 0° (versus 35° left). Significantly restricted and painful.
  • External Rotation (ER) in extension: 45° (versus 40° left).
  • Internal Rotation (IR) in 90° flexion: -10° (versus 30° left). Markedly restricted and painful, indicating significant posterior impingement from femoral retroversion and/or anterior impingement from reduced head-neck offset.
  • External Rotation (ER) in 90° flexion: 55° (versus 40° left).
• Trendelenburg Test: Positive on the right, indicating abductor weakness and/or poor mechanical advantage.

Neurological & Vascular Assessment

• Neurological examination of the right lower extremity was intact:
  • Motor strength 5/5 in all major muscle groups (hip flexors, extensors, abductors, adductors, knee flexors, extensors, ankle dorsiflexors, plantarflexors).
  • Sensation intact to light touch in L1-S1 dermatomes.
  • Deep tendon reflexes (patellar, Achilles) 2+ and symmetric bilaterally.
• Vascular examination was normal:
  • Strong and symmetric femoral, popliteal, dorsalis pedis, and posterior tibial pulses bilaterally.
  • Capillary refill brisk in all toes.

Overall, the clinical picture was consistent with sequelae of LCPD, characterized by significant pain, restricted range of motion, particularly internal rotation and abduction, and an abductor lurch, suggesting a complex femoral head and neck deformity leading to impingement and potential instability.

Imaging & Diagnostics

Radiographs

AP Pelvis, Frog-leg Lateral, Cross-table Lateral (Right Hip)
* AP Pelvis:
* Right femoral head appeared flattened, enlarged (coxa magna), and mushroom-shaped, with a clear loss of sphericity.
* Widening and shortening of the femoral neck were noted, leading to a reduced head-neck offset.
* The head-neck junction demonstrated bony prominence consistent with a cam-type deformity, particularly superolaterally.
* Lateral subluxation of the femoral head was evident, with reduced lateral femoral head coverage. The Epiphyseal Extrusion Index (EPI) was calculated at 35%.
* The neck-shaft angle (NSA) was measured at 110°, confirming coxa vara deformity (normal 125-135° in this age group).
* The Tönnis angle (acetabular roof angle) was 5°, indicating mild acetabular dysplasia/remodeling (normal <10°). The lateral center-edge (LCE) angle was 15° (normal >25°), further demonstrating inadequate lateral coverage.
* Articulotrochanteric distance was increased on the right, suggesting relative trochanteric overgrowth.
* Mild osteosclerosis and irregularity of the femoral head architecture, consistent with healed LCPD.
* Frog-leg Lateral & Cross-table Lateral:
* Demonstrated significant flattening of the anterior and superior femoral head.
* The alpha angle was measured at 75° (normal <55°), confirming significant cam-type impingement.
* Evidence of increased femoral retroversion was suggested by the anterior position of the lesser trochanter on the cross-table lateral view and the markedly restricted internal rotation clinically.

Computed Tomography (CT) Scan

Indications: To precisely quantify the complex 3D deformity of the proximal femur, including version, and to assess articular congruity and impingement zones. Crucial for surgical templating.
* Findings (3D Reconstruction & Axial Slices):
* Confirmed severe flattening and enlargement of the femoral head (coxa magna).
* Marked reduction in head-neck offset circumferentially, most pronounced anterosuperiorly.
* Femoral neck-shaft angle: 110° (confirming coxa vara).
* Femoral version: 10° of femoral retroversion (normal anteversion 10-20° in pediatric population). This directly correlated with the restricted internal rotation clinically.
* Acetabular morphology: Mild acetabular remodeling with some posterior wall deficiency, but primarily a femoral-sided deformity.
* Articular cartilage: Appears thinned in weight-bearing areas, with focal areas of subchondral sclerosis but no gross collapse.
* Quantified the extent of impingement zones, showing both anterior and posterior impingement due to the combined retroversion and cam deformity.

Magnetic Resonance Imaging (MRI)

Indications: To evaluate the integrity of the articular cartilage, labrum, and identify any active inflammatory processes or avascular necrosis.
* Findings:
* Diffuse thinning of articular cartilage over the superior and anterior aspects of the femoral head, consistent with early degenerative changes.
* Labral fraying and partial tears noted anterosuperiorly and posterosuperiorly, likely secondary to chronic impingement.
* No acute signs of osteonecrosis or significant synovial inflammation.
* Small paralabral cyst noted anterosuperiorly.
* Effusion: Minimal intra-articular fluid.

Templating

• Utilizing specialized digital templating software, a comprehensive pre-operative plan was developed.
• Goals:
  • Increase the neck-shaft angle to improve lateral coverage and abductor mechanics.
  • Correct femoral retroversion to improve internal rotation and reduce impingement.
  • Restore a more spherical femoral head and improve head-neck offset.
  • Improve articular congruity.
  • Address leg length discrepancy.
• Simulated Osteotomy:
  • A subtrochanteric valgus-flexion (derotation) osteotomy was planned.
  • Valgus component: Calculated to increase the neck-shaft angle from 110° to 130°, requiring an opening wedge of approximately 20°. This would translate the femoral head medially.
  • Flexion (derotation) component: Calculated to internally rotate the distal femur by 25-30° to correct the 10° retroversion to a mild anteversion of 15-20°. This would improve the arc of internal rotation.
  • Implant selection: An AO pediatric 90° angled blade plate was chosen for stable fixation, considering the patient's age and bone quality. The blade insertion point and angle were precisely templated.
  • The planning also accounted for the potential need for a greater trochanteric advancement or osteotomy to further address impingement and optimize abductor leverage, which would be decided intra-operatively.

Differential Diagnosis

The clinical and radiographic findings are highly suggestive of sequelae from Legg-Calvé-Perthes disease requiring reconstructive surgery. However, in pediatric hip pain and deformity, several other conditions must be considered in the differential diagnosis.

Surgical Decision Making & Classification

The decision for operative intervention via a valgusflexion femoral osteotomy in this patient was based on several critical factors:

Indications for Operative Management

1. Persistent Pain: The patient experienced chronic, activity-limiting pain, refractory to conservative measures, indicating ongoing joint pathology and impingement.
2. Functional Limitation: Significant restriction in activities of daily living and participation in sports due to limited hip range of motion, particularly internal rotation and abduction, and the presence of an abductor lurch.
3. Radiographic Deformity:
   • Femoral Head Asphericity (Stulberg Group IV): The mushroom-shaped, flattened femoral head (coxa magna) leads to incongruity.
   • Femoral Head Subluxation/Extrusion: The EPI of 35% and LCE angle of 15° indicated inadequate lateral coverage of the femoral head, increasing shear forces and predisposition to further degeneration.
   • Coxa Vara (NSA 110°): This reduces the abductor lever arm, contributing to the Trendelenburg gait and abductor weakness.
   • Femoral Retroversion (10°): This was a primary contributor to the severe restriction in internal rotation and anterior impingement.
   • Cam-type Deformity (Alpha Angle 75°): The reduced head-neck offset further exacerbated impingement.
4. Early Degenerative Changes: MRI findings of articular cartilage thinning and labral tears confirmed ongoing damage to the joint, necessitating intervention to prevent further progression to osteoarthritis.
5. Failure of Conservative Management: The patient had already undergone conservative treatment with bracing during the active phase of LCPD without achieving a favorable anatomical outcome.

Surgical Classification & Goals

The patient's condition, as sequelae of LCPD, can be classified using the Stulberg Classification , which describes the sphericity and congruity of the healed femoral head:
* Stulberg Group I: Spherical, congruent.
* Stulberg Group II: Spherical, congruent, but some flattening of the femoral head.
* Stulberg Group III: Aspherical, congruent (ovoid head fitting ovoid socket).
* Stulberg Group IV: Aspherical, incongruent (flattened head not fitting socket well).
* Stulberg Group V: Aspherical, incongruent with severe flattening and degenerative changes.

Our patient presented with a femoral head morphology consistent with Stulberg Group IV , indicating an aspherical and incongruent joint with evidence of impingement and subluxation. This morphology is strongly associated with poor long-term outcomes without surgical intervention.

The primary goals of the valgusflexion (derotation) femoral osteotomy were:
1. Re-center the Femoral Head: By increasing the neck-shaft angle (valgus), the femoral head is translated medially into the acetabulum, improving lateral coverage and articular congruity.
2. Reduce Femoral Impingement:
* Valgus: Improves head-neck offset in the superior aspect and can reduce cam-type impingement.
* Flexion (Derotation): Corrects retroversion, thereby moving the anteriorly prominent part of the femoral neck away from the anterior acetabular rim during flexion and internal rotation, and improving the arc of internal rotation.
3. Improve Abductor Mechanics: Increasing the neck-shaft angle lengthens the abductor lever arm, improving muscle efficiency and reducing the abductor lurch.
4. Optimize Articular Load Distribution: By improving coverage and congruity, the load across the hip joint is distributed more evenly, potentially slowing the progression of osteoarthritis.
5. Improve Range of Motion and Function: Alleviate pain and allow for greater participation in age-appropriate activities.
6. Address Leg Length Discrepancy: The valgus component of the osteotomy will result in a slight lengthening of the affected limb, which helps in reducing the existing LLD.

Non-operative vs. Operative Rationale

Non-operative management, primarily observation and symptomatic treatment, had failed to halt the progression of deformity or alleviate symptoms. Given the child's age, significant residual growth potential, the severity of the deformity (Stulberg IV, coxa vara, retroversion, subluxation), and the presence of early degenerative changes, intervention was deemed necessary to salvage the joint and improve long-term functional outcomes. A valgusflexion osteotomy directly addresses the complex femoral deformity, which is the primary driver of the patient's symptoms and joint degeneration.

Surgical Technique / Intervention

Pre-operative Planning Review

Detailed pre-operative planning was paramount. The CT scan provided precise measurements for the valgus angle (20° increase in NSA) and the rotational correction (25-30° internal rotation to correct 10° retroversion to 15-20° anteversion). The osteotomy level was planned subtrochanterically to allow for adequate bone stock for fixation and to preserve the greater trochanteric apophysis, unless specific trochanteric management was indicated. An AO pediatric 90° angled blade plate was selected.

Patient Positioning

The patient was positioned supine on a radiolucent operating table. The pelvis was leveled, and care was taken to pad all pressure points. The affected limb was draped free to allow for full range of motion assessment intra-operatively. A C-arm fluoroscopy unit was positioned to allow for clear AP and lateral views of the hip and proximal femur.

Surgical Approach

A direct lateral approach was utilized. A longitudinal incision, approximately 12-15 cm in length, was made over the lateral aspect of the proximal femur, centered over the planned subtrochanteric osteotomy site.
1. The skin and subcutaneous tissues were incised.
2. The fascia lata was incised longitudinally, and the vastus lateralis muscle was split or anteriorly retracted from the intermuscular septum to expose the lateral cortex of the proximal femur, from just distal to the greater trochanter down to the planned osteotomy level.
3. Care was taken to identify and protect the branches of the femoral nerve supplying the vastus lateralis.

Osteotomy Execution

1. Guide Wire Insertion: Under C-arm guidance (AP and lateral views), a K-wire was inserted into the femoral neck and head fragment, parallel to the planned blade insertion trajectory for the angled blade plate. This wire served as a preliminary guide for blade placement and helped maintain rotational control of the proximal fragment.
2. Marking and Measurement: The planned osteotomy level was marked on the lateral cortex. Using the pre-operative templating, the specific angles for valgus and derotation were transferred to the bone.
3. Osteotomy Cuts:
   • A transverse or slightly oblique osteotomy was performed subtrochanterically using an oscillating saw. This cut typically began at the planned blade insertion site and extended across the femur.
   • For the valgus correction , an opening wedge osteotomy was performed. After the initial transverse cut, a second cut was made on the lateral cortex, diverging distally to create an opening wedge, the size of which was determined by the templated 20° correction. The medial cortex was carefully osteotomized but left partially intact initially to act as a hinge, or fully cut if a complete wedge was removed.
   • For the flexion (derotation) correction , after the osteotomy was completed, the distal femoral fragment was internally rotated relative to the proximal fragment. A K-wire was drilled longitudinally into the distal fragment to serve as a rotational reference. The proximal fragment's rotation was maintained by the initial guide wire or by manual control. The desired 25-30° of internal rotation was achieved by aligning the distal fragment reference wire with the new desired orientation.
4. Correction and Fixation:
   • The osteotomy was carefully manipulated to achieve the desired valgus and rotational correction. The lateral opening wedge was maintained.
   • The 90° angled blade plate was then inserted. The blade was carefully malleted into the pre-drilled path in the proximal fragment (femoral head and neck), ensuring its tip was positioned appropriately in the femoral head on AP and lateral C-arm views, avoiding the articular surface.
   • Once satisfactory position of the blade in the proximal fragment was confirmed, the plate was secured to the lateral cortex of the distal femoral shaft using appropriate cortical screws. Compression was applied across the osteotomy site if a closing wedge was performed, or maintained in the case of an opening wedge, often with bone grafting.
   • Bone Grafting: For the opening wedge valgus osteotomy, autogenous cancellous bone graft (harvested from the iliac crest) was packed into the lateral osteotomy gap to promote union and provide additional stability.
5. Intra-operative Assessment:
   • C-arm Fluoroscopy: AP and lateral images were obtained to confirm:
     • Corrected neck-shaft angle (now approximately 130°).
     • Adequate femoral head coverage.
     • Satisfactory femoral version (assessed by the relative position of the lesser trochanter on the lateral view and comparison to pre-operative films or an intra-operative template).
     • Proper placement of the blade and screws, ensuring no intra-articular penetration.
   • Clinical ROM: The hip was put through a full range of motion. A significant improvement in internal rotation and abduction was noted, with resolution of the previously identified impingement at end-range flexion and internal rotation. The new arc of motion was smooth and pain-free. Leg length was re-checked and showed slight lengthening of the operated limb, reducing the LLD.
6. Adjunctive Procedures (Intra-operative Decision): In this case, the hypertrophied greater trochanter was impinging on the ilium during abduction. Therefore, a greater trochanteric osteotomy and distal advancement (approximately 1.5 cm) was performed and secured with two cancellous screws. This further improved abductor mechanics and prevented superior impingement.
7. Wound Closure: After copious irrigation, the vastus lateralis was reapproximated (if split) or allowed to fall back into place. The fascia lata was closed. Subcutaneous tissues and skin were closed in layers. A sterile dressing was applied.

Post-Operative Protocol & Rehabilitation

The post-operative protocol was designed to protect the osteotomy and fixation while promoting healing and gradual restoration of function.

Immediate Post-Operative Period (Day 0-7)

• Pain Management: Multimodal analgesia including epidural/nerve block, NSAIDs, and opioid analgesics as needed.
• Neurovascular Checks: Frequent neurovascular assessment of the lower extremity to monitor for complications.
• Immobilization: The limb was placed in a custom abduction brace or a soft hip spica cast for comfort and to limit extreme movements in younger children, though with stable plate fixation, a cast may not be strictly necessary beyond initial protection.
• Weight Bearing: Strict non-weight bearing (NWB) on the operated limb using crutches or a walker. Patient and family education on NWB status was critical.
• Physical Therapy (PT) Consult:
  • Bed mobility training and transfers.
  • Isometric quadriceps and gluteal muscle contractions.
  • Ankle pump exercises to prevent deep vein thrombosis.
  • Upper extremity strengthening to prepare for crutch ambulation.

Early Rehabilitation Phase (Weeks 1-6)

• Weight Bearing: Continue NWB on the operated limb.
• Range of Motion:
  • Gentle passive range of motion (PROM) within protected limits, avoiding extreme flexion (>90°) and internal rotation, which could stress the osteotomy site.
  • Active-assisted range of motion (AAROM) as pain allowed.
• Strengthening:
  • Continue isometric exercises for hip and thigh muscles.
  • Introduce gentle active-assisted hip flexion, extension, abduction, and adduction exercises, with careful attention to pain and avoiding resistance.
  • Core stability exercises.
• Mobility: Progress with crutch ambulation, focusing on proper gait mechanics without weight bearing.

Intermediate Rehabilitation Phase (Weeks 6-12)

• Radiographic Assessment: X-rays at 6-8 weeks to assess for early signs of osteotomy union.
• Weight Bearing Progression:
  • If radiographic signs of early union are present, progress to touch-down weight bearing (TDWB) or partial weight bearing (PWB) with crutches (up to 25% body weight).
  • Gradually increase weight bearing as union progresses and pain allows.
• Range of Motion: Increase intensity of AROM and PROM exercises. Focus on regaining full, pain-free hip range of motion, particularly internal rotation and abduction, which were previously restricted.
• Strengthening:
  • Begin light resistance exercises for hip abductors, adductors, flexors, and extensors.
  • Introduction of closed-chain exercises (e.g., mini-squats with minimal weight bearing on the operated leg).
• Balance & Proprioception: Introduce balance exercises.

Advanced Rehabilitation Phase (Months 3-6)

• Radiographic Assessment: X-rays at 3-4 months to confirm further osteotomy union.
• Weight Bearing:
  • Progression to full weight bearing (FWB) when radiographs confirm solid osteotomy union.
  • Discontinuation of crutches/walking aids once confident, pain-free FWB is achieved with a non-antalgic gait.
• Strengthening:
  • Progress to more advanced resistance training for all hip and core muscles.
  • Functional exercises: lunges, step-ups, single-leg stance.
• Endurance & Conditioning: Stationary cycling, swimming, elliptical trainer to improve cardiovascular fitness and muscular endurance.
• Gait Training: Focus on normal gait mechanics without assistive devices.

Return to Activity & Long-Term Follow-up (Months 6-18)

• Return to Sport: Gradual return to light, low-impact activities first (e.g., jogging). High-impact sports are typically allowed after 9-12 months, once full strength, range of motion, and confidence are restored, and osteotomy union is robust.
• Hardware Removal: Elective hardware removal is generally recommended in pediatric patients, typically 12-18 months post-surgery, after complete osteotomy union and bone remodeling to prevent stress shielding, refracture at stress risers, and implant prominence. This decision is individualized based on symptoms, patient age, and surgeon preference.
• Ongoing Monitoring: Regular clinical and radiographic follow-up to monitor hip health, assess for signs of early osteoarthritis, and ensure continued functional improvement.

Pearls & Pitfalls (Crucial for FRCS/Board Exams)

Pearls

1. Meticulous Pre-operative Planning is Paramount:
   • CT with 3D Reconstructions: Essential for accurate assessment of femoral version, neck-shaft angle, head-neck offset, and identification of impingement zones. Do not rely solely on plain radiographs for complex 3D deformities.
   • Digital Templating: Use templating software to precisely calculate the required angular and rotational corrections. This allows for simulation of the osteotomy and selection of the appropriate implant (e.g., angled blade plate, locking plate).
   • Clinical Correlation: Always correlate imaging findings with the clinical examination, particularly restricted ROM and impingement patterns.
2. Intra-operative Rotational Control:
   • Use K-wires drilled into both the proximal and distal fragments as rotational guides. This is critical for accurate derotation and avoiding malrotation.
   • Measure the degree of internal and external rotation before and after osteotomy on the C-arm to ensure desired correction.
3. Intra-operative Clinical Assessment of ROM:
   • After osteotomy and temporary fixation, move the hip through its full range of motion. Confirm improved internal rotation, abduction, and resolution of impingement. This is a real-time validation of your correction.
   • Check leg lengths after fixation.
4. Stable Fixation:
   • Angled blade plates (e.g., 90° AO blade plate) or pediatric locking plates provide robust, rigid fixation crucial for osteotomy union and early mobilization.
   • Ensure proper blade/screw placement within the femoral head/neck to avoid articular penetration and maximize purchase.
5. Bone Grafting for Opening Wedge Osteotomies:
   • Autogenous cancellous bone graft (e.g., from the iliac crest) is highly recommended for opening wedge osteotomies to promote rapid and robust union, preventing delayed union or non-union.
6. Concomitant Trochanteric Osteotomy/Advancement:
   • In Perthes sequelae, the greater trochanter is often overgrown, contributing to impingement (trochanteric-pelvic) and reducing abductor leverage. Consider a concomitant greater trochanteric osteotomy and distal advancement to optimize abductor mechanics and prevent impingement.
7. Address All Components of the Deformity: A valgusflexion osteotomy is powerful because it addresses coxa vara (valgus), retroversion (flexion/derotation), and often improves head coverage and reduces impingement simultaneously.

Pitfalls

1. Inadequate Correction:
   • Residual Impingement: Failure to achieve sufficient valgus or derotation will result in persistent pain, limited ROM, and continued cartilage damage, leading to early osteoarthritis. This is the most common reason for revision.
   • Residual Subluxation: Inadequate valgus can leave the head poorly covered, predisposing to further degeneration.
2. Overcorrection:
   • Excessive Valgus: Can lead to a relative lengthening of the limb, excessive anteversion, or medialization of the head causing a form of pincer impingement against the acetabular floor.
   • Excessive Anteversion: Can lead to anterior hip instability or excessive toe-in gait.
3. Malunion/Non-union:
   • Unstable Fixation: Inadequate plate selection or poor surgical technique can lead to loss of fixation, non-union, or malunion.
   • Large Gap without Grafting: Opening wedge osteotomies with large gaps require bone graft to bridge the defect and promote healing; failure to do so increases the risk of non-union.
   • Infection: Can lead to non-union and significant morbidity.
4. Neurovascular Injury:
   • Sciatic Nerve: Risk during posterior retraction or if using a posterior approach.
   • Femoral Nerve/Artery/Vein: Risk during anterior exposure or excessive retraction.
   • Lateral Femoral Cutaneous Nerve: Risk of injury during the lateral approach, leading to meralgia paresthetica.
5. Hardware-Related Complications:
   • Implant Prominence/Irritation: Especially in thin pediatric patients, leading to pain and necessitating early removal.
   • Hardware Failure: Breakage or loosening, often due to premature weight-bearing or inadequate union.
   • Intra-articular Penetration: Blade or screw entering the joint, leading to chondral damage.
6. Post-operative Stiffness/Heterotopic Ossification:
   • Prolonged immobilization or excessive soft tissue trauma can contribute to stiffness or HO formation, limiting the achieved ROM.
7. Refracture:
   • Risk exists, particularly after hardware removal, if the bone is not fully remodeled and strengthened. Patients need to protect the limb post-hardware removal.
8. Progression of Degenerative Changes:
   • While surgery aims to slow progression, it cannot reverse pre-existing cartilage damage. Patients must be counselled on the long-term risk of secondary osteoarthritis, potentially requiring future arthroplasty.