Arthroscopic Drilling and Fixation of Osteochondritis Dissecans

 

 

 

DEFINITION

Osteochondritis dissecans (OCD) is described as a focal, idiopathic alteration of subchondral bone with risk for instability and disruption of adjacent articular cartilage that may result in premature

osteoarthritis.25

 

 

ANATOMY

 

The most common location for OCD lesions to occur is in the knee; more specifically, on the lateral aspect of the medial femoral condyle.

 

The morphology of the OCD in this anatomic position varies and can appear as an initial softening of the subchondral bone and overlying articular cartilage, which can progress to early articular cartilage separation and later osteochondral separation (FIG 1).

 

PATHOGENESIS

 

Although the exact pathogenesis of OCD remains unclear, several hypotheses about the etiology of OCD have been proposed—ischemia, trauma, accessory centers of ossification, and genetic factors.

 

Ischemia

 

 

In 1870, Sir James Paget had described what was later thought to be OCD as “quiet necrosis.”24 Green

and Banks14 also theorized that OCD was due to ischemia of subchondral bone leading to the development of OCD.

 

Later studies on the epiphyseal artery construct, however, would conclude that this hypothesis is less likely to explain the etiology.

 

Microtrauma

 

 

Fairbank's12 early work described trauma as an etiology for OCD. Smillie27 strongly supported Fairbank's “tibial spine” theory for the etiology of OCD. Although this may offer an explanation for the classic location on the lateral aspect of the medial femoral condyle, it does not account for other locations of OCD in the knee.

 

A theory of repetitive microtrauma is appealing given that multiple studies have shown up to 60% of patients with OCD report being involved in sporting activities.3, 15, 21

 

 

 

FIG 1 • Showing three common morphologies of OCD lesions of the knee. A. Ballotable, intact cartilage lesion. B. Fissured “locked door” lesion. C. Hinged trap door lesion.

 

 

Reports of acute traumatic events that lead to delayed development of lesions that resemble OCD have been reported in the knee and elbow.9, 13, 28

 

Accessory centers of ossification

 

 

The one hypothesis that may unite all previous evidence is that of epiphyseal endochondral ossification described by Ribbing.26

 

These “accessory centers of ossification” were described by Ribbing26 and shown to occur in the classic location of the medial femoral condyle.

 

Genetic

 

 

Although a solitary lesion is the most common finding of OCD, cases of joint bilaterality, multiple lesions in a single joint, and reports of OCD in twin studies have provided support for a hypothesis of genetic predisposition.

 

NATURAL HISTORY

 

Hughes et al16 documented the natural history of skeletally immature OCD of the knee through serial magnetic resonance imaging (MRIs) over a 5-year period, which they correlated with arthroscopy and clinical outcomes.

 

In this small series, they demonstrated that all lesions with intact cartilage will likely heal with conservative treatment; however, if the lesion shows evidence of cartilage breakdown or subchondral bone fragmentation, it

loses its mechanical support and may progress to further breakdown resulting in extrusion into the joint.16

 

PATIENT HISTORY AND PHYSICAL FINDINGS

 

The presentation of OCD of the knee is variable, and the symptomatology is in large part due to the stage of the lesion when the particular symptoms present.

 

A stable lesion which remains in situ may present as nonspecific knee pain that is poorly localized by the patient, externally rotated gait, and a possible effusion.29

 

A lesion that has progressed to instability may become a “trap door”-type lesion with mobility or a loose body. Both lesion types may present with mechanical symptoms that may be described as a “catching” or “locking” sensation.

 

In 1967, Wilson29 describes a clinical examination finding which he suggests is diagnostic of OCD of the knee: “[With the patient] in the supine position, the knee on the affected side is flexed through about 90° and the tibia is medially rotated. The knee is then gradually extended and at a point of about 30° short of full extension

the [patient] will complain of pain over the anterior part of the medial femoral condyle. Lateral rotation of the tibia relieves this pain immediately.”

 

However, Wilson sign has been shown to be unreliable and nonspecific.8

 

 

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IMAGING AND OTHER DIAGNOSTIC STUDIES

 

Imaging protocols have received close attention in the literature as a result of the varied success of nonoperative treatment. The goals of imaging are to characterize the lesion, determine the prognosis of nonoperative management, and monitor the healing of the lesion.

 

Radiographs are useful for making the diagnosis of OCD and should be the first imaging modality of choice, as they usually characterize and localize the lesion and rule out other bony pathology of the knee region. In a significant number of cases, however, OCD lesions may not be readily apparent on plain radiographs.

 

 

Imaging workup begins with plain radiographs, including anteroposterior (AP), tunnel, and lateral views (FIG 2A-C).

 

A Merchant view should be included to best reveal any OCD lesions of the patella or trochlea.

 

MRI is most useful for determining the size of the lesion and the status of the cartilage and subchondral bone in addition to further characterizing the OCD lesions (FIG 2D-F).

 

 

The extent of bony edema, the presence of a high-signal zone beneath the fragment, and the presence of other loose bodies are also important findings on MRI. Arthroscopy continues to be the gold or reference

 

standard for diagnosing stability.4 Scintigraphy and computed tomography (CT)

 

Although CT can better differentiate bone contour and congruency, this are rarely ordered especially in juvenile cases of OCD.

 

 

 

FIG 2 • Three-view series of OCD lesion: AP (A), tunnel view (B), and lateral view (C). MRI sequence of OCD: coronal (D), axial (E), and sagittal slice (F). Red arrows point to OCD lesion.

 

 

Similarly, technetium bone scans have been employed to provide information about the biologic capacity of an OCD lesion to heal. However, with the advent of MRI and its ability to be used without exposure to radiation yet still provide quality images of OCD lesions, scintigraphy is less commonly used.

 

Use of ionizing radiation in OCD lesions should be carefully considered, as other imaging options may provide excellent diagnostic and prognostic information with none or minimal exposure to radiation.

 

 

DIFFERENTIAL DIAGNOSIS

Irregular ossification

Acute osteochondral fractures Meniscal injuries

 

 

NONOPERATIVE MANAGEMENT

 

An initial course of nonoperative management is the treatment of choice for skeletally immature children with small intact lesions with the goal of nonoperative intervention to promote healing in the subchondral bone and potentially prevent chondral collapse, subsequent fracture, and crater formation.

 

Controversy exists regarding the ideal nonoperative management for these patients. Clinicians who adhere to treating the subchondral bone as the primary source of pathology favor a period of immobilization. Those whose focus is on

 

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the articular cartilage as a source of pathology tend to favor mobilization.

 

 

Table 1 Three-Phase Approach to Nonoperative Management of Skeletally Immature Osteochondritis Dissecans

 

Knee immobilization in a hinged brace. The patient may walk with the hinged brace locked in extension. The brace may be unlocked to work on range of motion for 5 minutes five times per day.

Phase I (wk 1-6)

 

 

Phase II (wk 6-12)

If the patient is pain-free and radiographs show signs of healing after 6 weeks, he or she is allowed to begin weight bearing without immobilization and to begin a physical therapy protocol to improve knee range of motion and quadriceps and hamstring strength.

 

Phase III* (wk 8-12)

Running, jumping, and cutting sports are permitted under close observation. High-impact activities and activities that might involve shear stress to the knee should be restricted until the child has been pain-free for several months and the radiographs show a healed lesion.

 

*This phase begins typically 3 months after treatment and is instituted if the patient continues to remain pain-free and shows radiographic evidence of healing.

 

 

The options for immobilization include casting, bracing, and standard knee immobilizers.

 

We recommend a three-phase approach to the nonoperative management of OCD lesions (Table 1).

 

SURGICAL MANAGEMENT

 

The goals of operative treatment are to promote healing of the native articular cartilage and subchondral bone when possible, to maintain joint congruity, to rigidly fix unstable fragments, and to replace osteochondral defects with cells that can replace and grow cartilage.

 

It is widely accepted that operative treatment should be considered for patients with unstable or detached lesions and in patients whose lesions have not resolved with an appropriate period of nonoperative management, especially in those approaching skeletal maturity.

 

Operative treatment is recommended if one or more of the following conditions are met:

 

 

 

 

 

Persistently symptomatic juvenile lesions Presence of symptomatic loose bodies Predicted physeal closure within 1 year Evidence of fragment detachment/instability

 

Optimal surgical treatment provides a stable construct of subchondral bone, calcified tidemark, and cartilage repair with viability and biomechanical properties equivalent to or similar to native hyaline cartilage.

 

Preoperative Planning

 

Careful preoperative evaluation and preparation are always imperative to the success of treatment.

 

All imaging studies obtained before surgery should be reviewed. If the displaced fragment has a relatively large osseous component, then plain radiographs will usually demonstrate the lesion.

 

Radiographs do not demonstrate the actual size of the cartilaginous component. To demonstrate the cartilaginous component, MRI may be required to determine the extent of the lesion. Any other lesion noted on imaging studies should likewise be addressed.

 

A thorough physical examination should be performed under anesthesia.

 

Positioning

 

For arthroscopic procedures, the position largely depends on the surgeon's preference. A variety of positions can be used:

 

 

The leg can be placed in a leg holder on the operating table with the knee joint past the end of the operating table, thus allowing the knee to flex 90 degrees and the lower leg to hang freely.

 

The leg can be placed supine on the operating table, with the hip flexed and the knee flexed 90 degrees. The knee can be flexed, and the lower leg can, in this case, hang freely over the side of the operating table.

 

The leg can be placed supine on the operating table, with the hip flexed and the knee flexed 90 degrees, using a thigh post and foot post to hold the leg in this position. The lower leg in this case may remain on the flat table and does not need to hang off the end of the table.

 

Approach

 

Standard arthroscopic parapatellar portals are initially used (FIG 3A).

 

 

Key: Accessory portals may be created higher or lower to the standard parapatellar portals if the lesion is excessively large or in an atypical location.

 

Transarticular drilling can be used for intact lesions, but it is particularly valuable when the lesion is detached, partially detached, or unstable (FIG 3B).

 

Retroarticular drilling is reserved for cases with intact lesions (FIG 3C).

 

 

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FIG 3 • Standard arthroscopic portals are used for arthroscopic drilling techniques. A. Accessory portals can be used for visualizing or treating lesions of the patellotrochlear interval. B. Transarticular drilling of OCD lesion. C. Retroarticular drilling of OCD lesion.

 

TECHNIQUES

 

• Transarticular Drilling of Osteochondritis Dissecans Lesion

   

  This procedure can be completed with or without exsanguinating the knee and applying a tourniquet depending on surgeon preference.

   

  An anterolateral portal and anteromedial portals are made for visualization and instrumentation.

   

  A complete arthroscopic inspection of the knee is performed. Any other pathologies in the knee are recorded and treated accordingly.

   

  The lesion is identified (TECH FIG 1A).

   

  A 0.45- or 0.62-inch Kirschner wire is positioned perpendicular to the lesion (TECH FIG 1B). The portal used depends on the location of the lesion.

   

  The key is to keep the Kirschner wire as perpendicular as possible. Additional portals as well as varying the degree of knee flexion and extension may be used as needed to achieve adequate position.

   

   

   

  TECH FIG 1 • A. The knee is inspected and the lesion is identified. The solid arrow shows the intact cartilage side and the open arrow shows the OCD side. B. A Kirschner wire is shown superimposed over a T1-weighted MRI. The arrow shows the direction of drilling. The smooth 0.62-inch Kirschner wire should be kept as perpendicular to the lesion as possible to prevent undermining the defect. C,D. The appearance of fat or blood demonstrates that subchondral bone has been penetrated.

   

   

  The drilling is performed under arthroscopic visualization. Having the radiographs and MRI images in the operating theatre can be used as visual aids to confirm the location and orientation of drilling of the lesion.

   

  Appropriate depth of penetration is confirmed by the efflux of blood or fat from the drilled holes (TECH FIG 1C,D).

   

  The drilling should be performed through the calcified tide-mark in immature patients, taking care not to penetrate the physis.

• Retroarticular Drilling of Osteochondritis Dissecans Lesion

   

  This procedure can be completed with or without exsanguinating the knee and applying a tourniquet depending on surgeon preference.

   

  Anterolateral and anteromedial portals are made for visualization and instrumentation.

   

  A complete arthroscopic inspection of the knee is performed. Any other pathologies in the knee are recorded and treated accordingly.

   

  Once complete inspection has been performed, a 0.62-inch Kirschner wire is directed toward the lesion in a proximal to distal direction with fluoroscopic guidance and a guide to help maintain an appropriate angle.

   

  The starting point of the Kirschner wire is immediately distal to the physis to avoid any damage.

   

   

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  The Kirschner wire is slowly advanced through the subchondral bone, taking care not to penetrate the articular cartilage.

   

  The Kirschner wire is kept as perpendicular to the lesion as possible.

   

  The position and depth of the Kirschner wires are confirmed using fluoroscopy.

   

  Kirschner wires are inserted through the lesion several millimeters apart as needed. A small drill guide that allows parallel pin placement may assist with repeat drilling.

   

  Final inspection of the knee is performed, and the Kirschner wires and instrumentation are removed.

   

  Closure of the knee is performed, and sterile dressing is applied before placing the knee in a knee immobilizer.

• Fixation of Unstable Osteochondritis Dissecans Lesion

Metallic or Bioabsorbable Screws

 

The entire lesion is assessed, and the bed is prepared. A débridement is performed until all granulation tissue and sclerotic bone beneath the flap is removed, and subchondral bone is reached.

 

In deep lesions, autograft or allograft cancellous bone grafting may be required to ensure that the hinged portion of the lesion is not recessed relative to the remaining unaffected cartilage within the knee.

 

The lesion is reduced into its bed and fixed with a variety of implants, such as cannulated screws or variable pitch screws. The fixation devices may be made of metal or bioabsorbable materials. The implant used depends on the surgeon's preference.

 

We prefer to use small metal double-ended threaded compression screws for hinged lesions in which there is appropriate subchondral support that allows for adequate screw thread to engage the subchondral progeny bone of the lesion. In some cases, the subchondral progeny bone may not be of adequate thickness to allow this type of fixation (TECH FIG 2).

 

Once the lesion is secured, drilling of the surrounding parent and progeny bone may be performed to augment healing.

Matchstick Technique

 

Anterolateral and anteromedial portals are made for visualization and instrumentation.

 

A complete arthroscopic inspection of the knee is performed. Any other pathologies in the knee are recorded and treated accordingly.

 

A 2.5-cm longitudinal incision is made approximately 1 cm medial to the tibial tubercle, which will be the site of bone stick harvest.

 

Using a microsaw, bone sticks are created and harvested from the tibia (TECH FIG 3A,B).

 

Using a large diameter cannula no. 1, the perforation of the focus is oriented and performed with a Steinmann pin that has a diameter similar to the internal diameter of cannula no. 2. Cannula no. 2 contains the bone stick and is introduced into cannula no. 1 (TECH FIG 3C,D).

 

 

 

TECH FIG 2 • Small metallic variable pitch compression screws are the authors' preferred choice for fixation used for hinged lesions— although many options are available.

 

The trocar is introduced into cannula no. 2 to introduce the bone stick into the center of the OCD lesion.

 

This step is repeated with as many bone sticks as need to obtain a secure rigid fixation of the OCD lesion.

Autologous Osteochondral Grafting

 

Anterolateral and anteromedial portals are made for visualization and instrumentation.

 

A complete arthroscopic inspection of the knee is performed, taking care to assess the position and size of the lesion, which is used to estimate the number of needed osteochondral plugs to harvest.

 

The bed of the lesion is inspected, and a débridement is performed to remove any granulation tissue and sclerotic bone.

 

The estimation of osteochondral plug length is based on preoperative MRI findings.

 

The number of osteochondral plugs are then harvested from non-weight-bearing aspects of the medial and/or lateral trochlea (TECH FIG 4).

 

 

 

TECH FIG 3 • Showing preparation of skeletally immature OCD lesion for autologous cortical bone stick tunnels (A), measuring of bone sticks being harvested from the tibia (B), (continued)

 

 

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TECH FIG 3 • (continued) tamping of 1- × 16-mm bone sticks (black arrow) into lesion (C), and showing cortical bone sticks (red arrows) in place with cartilaginous congruency (D).

 

 

 

TECH FIG 4 • A. Depth of lesion at midpoint (X). B. Length of bone plug and drill hole, which should be twice that of X.

 

 

Using a 4.5-mm mosaicplasty drill and delivery guide, the bone plugs are inserted into the center of the lesion—or various locations depending on the number of plugs used.

 

Care must be taken to ensure that the osteochondral plug is not proud and there is clear cartilage

congruence compared to the adjacent cartilage.

The joint is inspected before final closure.

The arthroscopic instrumentation is removed, and the arthroscopic portals are closed. The knee is placed in a hinged knee brace.

 

 

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PEARLS AND PITFALLS

 

 

POSTOPERATIVE CARE

Our postoperative rehabilitative protocol is outlined in Table 2.

 

 

OUTCOMES

Nonsurgical treatment is often regarded as the treatment of choice for small stable lesions in skeletally immature patients. Typically, a period of 3 to 6 months of nonoperative treatment is instituted, with numerous authors reporting a success rate of 50% to 94%.1, 2, 6, 7

Skeletally immature patients with wide open physes and no signs of instability on MRI are more likely to respond to nonoperative measures.

Drilling

Both retroarticular drilling and transarticular drilling appear to have very favorable short-term clinical outcomes. Transarticular drilling has been reported as successful in 91% to 100% of patients.2, 7, 19 Retroarticular drilling has similar success rates and been reported as 75% to 96% of cases.1, 11, 17

Edmonds et al11 in the largest OCD case series reviewed 59 knees in 53 children with retroarticular drilling after 6 months conservative management reported complete radiographic healing in only 75%

 

Surgical technique

• Careful review of all prior imaging modalities and a complete clinical

evaluation is performed before surgery.

Transarticular

drilling

• The Kirschner wires should be kept as perpendicular to the lesion as

possible to prevent undermining the lesion. This technique is indicated for intact OCD lesions.

Matchstick

technique

• Care should be taken when establishing the harvest site on the medial

aspect of the tibia to avoid and not compromise the insertion of the pes anserinus.

Autologous

osteochondral grafting technique

• To assure rigid fixation the graft should be passed into the normal

underlying subchondral bone as far it had been passed through the lesion and the interface.

 

Table 2 Rehabilitation Protocol following Fixation of Unstable Skeletally Immature Osteochondritis Dissecans

*Follow-up x-ray performed prior to phase III. If healed, phase III is initiated. If unhealed, phase

II is repeated.

††ROM, range of motion; WBAT, weight-bearing as tolerated.

 

of cases but found complete resolution of pain and full return to activities in all patients after treatment. However, 13% of patients did require a repeat surgery.

 

 

Phase I (wk 1-6)	1.	1. Use of hinged brace for 6 wk, locked in extension for walking
	2.	2. Home physical therapy: unlock or remove brace to perform ROM,
		straight-leg raises
	3.	3. WBAT with brace locked in extension
Phase II* (wk 6-	1.	1. Brace removed
12)	2.	2. WBAT without brace: activities of daily living, no running or jumping
	3.	3. Physical therapy ROM, straight-leg raises, modalities
Phase III†† (wk	1.	1. Weight-bearing exercises, sport-specific exercises
8-12)	2.	2. Gradual return to spot

 

 

 

Boughanem et al6 retrospectively reviewed 34 knees in 31 children treated with arthroscopic retroarticular drilling and noted that 95% of patients had radiologic improvement.

 

Kocher et al19 reviewed 30 knees in 23 patients treated with arthroscopic transarticular drilling after 6 months of conservative therapy. All patients who failed to respond to nonoperative measures were noted to have healed after drilling.

 

Screw fixation

 

 

Kouzelis et al20 reported successful fixation of unstable lesions in patients aged 14 to 26 years old using variable pitch screw fixation. In this small series of 10 patients, with a mean follow-up of 27 months, radiologic union was observed in 9/10 patients and return to previous level of activity was also seen in 9/10 patients.

 

In contrast to the variable pitch screw, Cugat et al10 report on a small series of 14 patients (15 knees), with OCD lesions using cannulated screws as a means of fixation. In this series, there was a mean

follow-up of 43 months, and Cugat et al10 reported good to excellent results in 93% of this series with minimal complications.

 

Matchstick technique

 

 

Navarro et al23 describe this technique in a series of 11 patients aged 11 to 20 years old with OCD,

with a mean follow-up of 48 months. With satisfactory results in 90% of cases, Navarro et al23 state the advantages of this technique include obviation of large incisions or arthrotomy, solid fixation, and no need for hardware removal.

Autologous osteochondral grafting

 

Miniaci and Tytherleigh-Strong22 report on a series of 20 patients (age range of 12 to 27 years) with OCD of the knee who underwent autogenous osteochondral grafting (mosaicplasty) technique. Similar to other reports using fixation with mosaicplasty,5, 18 the series of Miniaci and Tytherleight-Strong22

series showed excellent 1 year outcomes.

 

 

COMPLICATIONS

Primary complications include the potential failure to heal, especially in older adolescents treated nonsurgically.

The prognosis for OCD lesions is worse in those patients who have reached skeletal maturity.

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Patients who have been treated nonsurgically and have not shown progressive healing and those patients with large lesions that are approaching skeletal maturity are therefore treated surgically to promote healing.

 

 

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