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10. Pathology and Oncology MCQs

Practice Set 176 of 351

This practice set contains high-yield board review questions covering key concepts in 10. Pathology and Oncology. Each clinical scenario is designed to test your diagnostic and management skills relevant to this subspecialty.

Question 3501

Topic: 10. Pathology and Oncology

A 15-year-old boy presents with right distal femoral pain and swelling. Biopsy confirms high-grade osteosarcoma. Staging studies reveal no metastatic disease. He has completed several cycles of neoadjuvant chemotherapy, demonstrating a good response. What is the most crucial principle to ensure local tumor control during subsequent surgical resection?

. Achieve a wide surgical margin (>2 cm of healthy tissue circumferentially).
. Perform an intralesional resection to preserve as much bone as possible.
. Use cryoablation or radiofrequency ablation to augment tumor kill at the surgical margins.
. Administer additional intraoperative chemotherapy directly into the surgical bed.
. Rely primarily on the efficacy of neoadjuvant chemotherapy to sterilize the tumor margins.

Correct Answer & Explanation

. Achieve a wide surgical margin (>2 cm of healthy tissue circumferentially).

Explanation

For high-grade osteosarcoma, surgical resection with adequate margins is the cornerstone of local tumor control and significantly impacts patient survival.Achieving a wide surgical margin(>2 cm of healthy tissue circumferentially) (A) is paramount. A wide margin means removal of the tumor along with a cuff of normal surrounding tissue, ensuring that no microscopic tumor cells are left behind. This is the gold standard for oncologic resection of sarcomas. Intralesional resection (B) is contraindicated for high-grade sarcomas due to very high rates of local recurrence. Cryoablation or radiofrequency ablation (C) are adjunctive therapies but not substitutes for achieving a wide surgical margin in curative resections. Administering intraoperative chemotherapy (D) is not a standard or proven method for local tumor control in osteosarcoma. Relying primarily on neoadjuvant chemotherapy to sterilize margins (E) is incorrect; while chemotherapy improves tumor necrosis, it does not eliminate the need for a definitive surgical resection with wide margins.

Question 3502

Topic: Bone Tumors

A 3-year-old child is diagnosed with congenital pseudarthrosis of the tibia (CPT). Radiographs show a sclerotic, atrophic non-union in the middle third of the tibia. He has a history of multiple casting attempts that have failed. What is the most critical factor influencing the high failure rate and difficult management of CPT?

. Associated fibrous dysplasia of the tibia.
. Underlying neurofibromatosis type 1 (NF1).
. Inadequate initial immobilization techniques.
. Poor vascularity of the fracture site.
. Parental non-compliance with treatment protocols.

Correct Answer & Explanation

. Underlying neurofibromatosis type 1 (NF1).

Explanation

Congenital pseudarthrosis of the tibia (CPT) is one of the most challenging orthopedic conditions. While CPT is often associated with localized abnormal tissue, the most critical underlying factor for its high failure rate and difficult management is its strong association withNeurofibromatosis type 1 (NF1)(B). Approximately 50-90% of CPT cases are associated with NF1. The pathophysiology of CPT in NF1 is thought to involve aberrant osteoclast activation and abnormal mesenchymal tissue surrounding the pseudarthrosis, which inhibits normal bone healing. This underlying biological defect, rather than just poor vascularity (D), makes healing extremely difficult and prone to recurrence. Fibrous dysplasia (A) is not the primary or most critical underlying factor influencing CPT failure rates; NF1 is the major association. Inadequate initial immobilization (C) can contribute to failure, but the inherent biological problem of CPT, particularly with NF1, makes it prone to failure even with excellent immobilization. Parental non-compliance (E) is a general factor but not themost critical factor influencing the high failure rateof CPTitself.

Question 3503

Topic: 10. Pathology and Oncology

A 25-year-old male presents with a persistent painful lump on his left distal femur for 6 months, accompanied by intermittent fever and weight loss. Radiographs show a lytic lesion with an 'onion skin' periosteal reaction and soft tissue mass. Biopsy confirms Ewing's sarcoma. What is the most appropriate initial management approach?

. Wide surgical resection and reconstruction.
. Radiation therapy alone.
. Chemotherapy followed by local control (surgery +/- radiation).
. Amputation.
. Observation with serial imaging.

Correct Answer & Explanation

. Chemotherapy followed by local control (surgery +/- radiation).

Explanation

Ewing's sarcoma is a highly aggressive malignant bone tumor that commonly metastasizes early. It is highly sensitive to chemotherapy and radiation. The standard of care involves initial neoadjuvant chemotherapy to treat micrometastases and shrink the primary tumor, followed by definitive local control (surgical resection and/or radiation therapy), and then adjuvant chemotherapy. Wide surgical resection alone is often insufficient due to early metastasis. Radiation therapy alone may be used for local control but not as initial monotherapy. Amputation is a salvage procedure, not typically initial management. Observation is contraindicated. Therefore, chemotherapy followed by local control is the gold standard.

Question 3504

Topic: 10. Pathology and Oncology

A 17-year-old male is diagnosed with high-grade osteosarcoma of the distal femur following biopsy. Staging studies reveal no evidence of metastatic disease. According to standard osteosarcoma management protocols, which of the following is the most appropriate next step after diagnosis and before definitive surgery?

. Immediate wide en bloc resection
. Neo-adjuvant chemotherapy
. Adjuvant radiotherapy
. Amputation without further staging
. Observation with serial imaging

Correct Answer & Explanation

. Neo-adjuvant chemotherapy

Explanation

For high-grade osteosarcoma, even in localized disease without evidence of metastases, neo-adjuvant (preoperative) chemotherapy is a standard of care. It aims to reduce tumor burden, treat micrometastatic disease, and assess tumor response to chemotherapy, which guides postoperative management. Immediate wide en bloc resection without neo-adjuvant chemotherapy is not the standard. Adjuvant radiotherapy is generally reserved for positive surgical margins or unresectable disease. Amputation is a definitive surgery that may be considered after neo-adjuvant chemotherapy if limb salvage is not feasible. Observation is never appropriate for high-grade osteosarcoma.

Question 3505

Topic: 10. Pathology and Oncology

A 62-year-old female with a known history of metastatic breast cancer presents with acute onset severe back pain, progressive bilateral lower extremity weakness (3/5), and new urinary retention. MRI shows a large epidural metastasis at T11 causing severe spinal cord compression. She is hemodynamically stable. What is the MOST immediate and critical management step?

. Initiate high-dose intravenous corticosteroids.
. Emergent surgical decompression (laminectomy).
. Immediate commencement of palliative radiation therapy.
. Administer opioid analgesics and observe.
. Order a CT-guided biopsy of the lesion.

Correct Answer & Explanation

. Initiate high-dose intravenous corticosteroids.

Explanation

This patient presents with acute spinal cord compression due to metastatic disease, evidenced by severe back pain, progressive motor weakness, and bladder dysfunction. The most immediate and critical management step is to initiate high-dose intravenous corticosteroids (e.g., Dexamethasone 10-16 mg IV bolus, then 4 mg q6h). Corticosteroids reduce peritumoral edema, which can alleviate pressure on the spinal cord and preserve neurological function while definitive treatment is planned. While emergent surgical decompression or radiation therapy will be necessary, corticosteroids provide immediate relief and are often initiated even before the patient reaches the operating room or radiation oncology. Analgesics alone do not address the cord compression. A biopsy is important for definitive diagnosis but should not delay critical management of cord compression.

Question 3506

Topic: 10. Pathology and Oncology

A 17-year-old male is diagnosed with a high-grade osteosarcoma of the distal femur. Staging shows no evidence of metastatic disease. He undergoes neoadjuvant chemotherapy, followed by wide en bloc resection and limb salvage with an endoprosthetic reconstruction. Which of the following is the most important factor for long-term oncologic control and local recurrence prevention in this case?

. The choice of endoprosthesis (e.g., modular vs. custom).
. Achieving negative microscopic surgical margins (R0 resection).
. The patient's return to high-impact sports.
. The duration of adjuvant chemotherapy.
. The type of physical therapy rehabilitation program.

Correct Answer & Explanation

. Achieving negative microscopic surgical margins (R0 resection).

Explanation

For limb salvage surgery in osteosarcoma, achieving negative microscopic surgical margins (R0 resection) is the single most important factor for local tumor control and preventing local recurrence. Any residual tumor cells at the margin (R1 or R2 resection) significantly increase the risk of recurrence and negatively impact prognosis. While other factors like chemotherapy response, type of reconstruction, and rehabilitation are important for overall outcome and function, they do not supersede the critical importance of clear oncologic margins for disease control. The choice of endoprosthesis affects function and mechanical longevity, not oncologic control. Return to high-impact sports is a functional goal, not an oncologic one. Adjuvant chemotherapy duration is determined by protocol and response, and its efficacy relies on complete surgical removal of the primary tumor.

Question 3507

Topic: 10. Pathology and Oncology

A 16-year-old male is diagnosed with high-grade osteosarcoma of the proximal tibia, characterized by significant extra-osseous extension and involvement of the neurovascular bundle, but without distant metastasis. Chemotherapy has been initiated. When considering surgical options, which of the following factors would most strongly favor amputation over limb salvage, even with clear surgical margins achievable by either method?

. The patient's young age and potential for growth.
. The specific histological subtype of osteosarcoma.
. The extent of functional preservation anticipated after limb salvage.
. Proximity of the tumor to the knee joint, necessitating total knee replacement.
. The patient's desire to pursue competitive sports post-treatment.

Correct Answer & Explanation

. The extent of functional preservation anticipated after limb salvage.

Explanation

While obtaining clear surgical margins is paramount for oncologic control, the choice between limb salvage and amputation is heavily influenced by the anticipated functional outcome. Significant involvement of the neurovascular bundle or critical muscles, even if resectable with clear margins, may lead to a limb salvage procedure with very poor function, chronic pain, or neurological deficits. In such cases, a well-fitted prosthesis after amputation might offer superior functional quality of life compared to a non-functional or painful reconstructed limb. The patient's age and desire for sports are secondary considerations to the fundamental functional prognosis.

Question 3508

Topic: 10. Pathology and Oncology

A 15-year-old male presents with acute thigh pain after a minor trip. Radiographs show a purely lytic, expansile metaphyseal lesion of the distal femur with a pathologic fracture. MRI demonstrates multiple fluid-fluid levels. Biopsy reveals blood-filled spaces with septations. Which microscopic finding definitively differentiates telangiectatic osteosarcoma from an aneurysmal bone cyst (ABC)?

. Presence of multinucleated giant cells
. Fibrous septa lacking an endothelial lining
. Highly atypical, pleomorphic stromal cells producing osteoid
. USP6 gene rearrangement
. Extensive areas of hemosiderin-laden macrophages

Correct Answer & Explanation

. Highly atypical, pleomorphic stromal cells producing osteoid

Explanation

Telangiectatic osteosarcoma (TOS) closely mimics an aneurysmal bone cyst (ABC) clinically and radiographically (both show lytic lesions with fluid-fluid levels). The definitive differentiating feature is histological: in TOS, the septa contain highly malignant, pleomorphic cells producing sarcomatous osteoid. USP6 gene rearrangement is characteristic of primary ABCs, not TOS.

Question 3509

Topic: 10. Pathology and Oncology

A 30-year-old male presents with a slow-growing, painful mass near his knee joint. MRI reveals a soft-tissue mass adjacent to but not communicating with the joint capsule. A core needle biopsy shows a biphasic tumor with both epithelial and spindle cell components. Which chromosomal translocation is highly characteristic of this malignancy?

. t(11;22)(q24;q12)
. t(X;18)(p11;q11)
. t(12;16)(q13;p11)
. t(2;13)(q35;q14)
. t(9;22)(q34;q11)

Correct Answer & Explanation

. t(X;18)(p11;q11)

Explanation

The vignette describes a biphasic synovial sarcoma, which is characterized by the t(X;18)(p11;q11) chromosomal translocation resulting in the SYT-SSX fusion gene. t(11;22) is seen in Ewing sarcoma; t(12;16) in myxoid liposarcoma; t(2;13) in alveolar rhabdomyosarcoma; and t(9;22) in extraskeletal myxoid chondrosarcoma.

Question 3510

Topic: Bone Tumors

A 7-year-old girl presents with a limp and a leg length discrepancy. Radiographs reveal a ground-glass appearance in the proximal femur with a shepherd's crook deformity. Physical examination shows large, irregular hyperpigmented skin macules with jagged borders. Which of the following endocrine abnormalities is most commonly associated with this patient's syndrome?

. Hypothyroidism
. Precocious puberty
. Hyperparathyroidism
. Adrenal insufficiency
. Diabetes insipidus

Correct Answer & Explanation

. Precocious puberty

Explanation

Correct Answer: Precocious pubertyThe patient's presentation of polyostotic fibrous dysplasia, cafe-au-lait spots with irregular borders (Coast of Maine), and endocrine dysfunction is classic for McCune-Albright syndrome. This syndrome is caused by a post-zygotic somatic activating mutation in the GNAS gene, leading to constitutive activation of the Gs-alpha protein and subsequent overproduction of cAMP. The most common endocrine abnormality in McCune-Albright syndrome is precocious puberty, particularly in females. Other potential but less common endocrine issues include hyperthyroidism, growth hormone excess, and Cushing syndrome.

Question 3511

Topic: 10. Pathology and Oncology

A 25-year-old male with a history of multiple enchondromas presents with a rapidly enlarging, painful mass in his right thigh. Physical examination reveals multiple bluish, compressible subcutaneous nodules on his hands and forearms. What is the most likely diagnosis of the thigh mass, and what is the underlying syndrome?

. Fibrosarcoma in McCune-Albright syndrome
. Osteosarcoma in Ollier disease
. Chondrosarcoma in Maffucci syndrome
. Malignant peripheral nerve sheath tumor in Neurofibromatosis type 1
. Secondary osteosarcoma in Multiple Hereditary Exostoses

Correct Answer & Explanation

. Chondrosarcoma in Maffucci syndrome

Explanation

Correct Answer: Chondrosarcoma in Maffucci syndromeMaffucci syndrome is a rare, non-hereditary disorder characterized by multiple enchondromas (anarchic cartilage development) associated with multiple soft-tissue hemangiomas (the bluish, compressible subcutaneous nodules). Patients with Maffucci syndrome have a significantly higher risk of malignant transformation compared to those with Ollier disease (enchondromatosis alone), with up to 100% lifetime risk of malignancy, most commonly chondrosarcoma. The rapidly enlarging, painful mass in a patient with this history is highly suspicious for secondary chondrosarcoma.

Question 3512

Topic: Bone Tumors

A 14-year-old boy with polyostotic fibrous dysplasia presents with a progressive shepherd's crook deformity of the proximal femur and increasing thigh pain. What is the most appropriate surgical management to prevent impending fracture and correct the deformity?

. Curettage and packing with autologous cancellous bone graft
. Curettage and packing with allograft bone chips
. Valgus osteotomy stabilized with an intramedullary nail
. Valgus osteotomy stabilized with a dynamic hip screw (DHS) and plate
. Resection of the dysplastic segment and endoprosthetic reconstruction

Correct Answer & Explanation

. Valgus osteotomy stabilized with an intramedullary nail

Explanation

Correct Answer: Valgus osteotomy stabilized with an intramedullary nailIn fibrous dysplasia, the normal bone is replaced by weak, woven bone and fibrous tissue. Bone grafting (autograft or allograft) is generally contraindicated because the grafted bone is rapidly resorbed and replaced by dysplastic host bone. For a shepherd's crook deformity (severe varus of the proximal femur), the biomechanically superior treatment is a valgus osteotomy to restore the mechanical axis, stabilized with an intramedullary device (like a reconstruction nail). Intramedullary nails are preferred over plates and screws (like a DHS) because plates create a stress riser at the end of the plate in the weak dysplastic bone, leading to a high risk of peri-implant fracture.

Question 3513

Topic: 10. Pathology and Oncology

A 28-year-old woman undergoes a pelvic radiograph following a minor fall. The radiograph shows numerous small, well-defined, symmetric sclerotic foci clustered around the periarticular regions of the pelvis and proximal femurs. She is completely asymptomatic. What is the most appropriate next step in management?

. Bone scintigraphy to rule out metastatic disease
. Open biopsy of a sclerotic lesion
. Serum calcium, phosphate, and alkaline phosphatase levels
. Reassurance and no further intervention
. Prophylactic bisphosphonate therapy

Correct Answer & Explanation

. Reassurance and no further intervention

Explanation

Correct Answer: Reassurance and no further interventionThe radiographic finding of numerous small, symmetric, periarticular sclerotic foci in an asymptomatic patient is classic for Osteopoikilosis (spotted bone disease). It is an autosomal dominant benign bone dysplasia (often linked to LEMD3 mutations) characterized by anarchic development of dense bone islands. It is entirely benign, asymptomatic, and does not undergo malignant transformation. Therefore, the most appropriate management is reassurance. Extensive workup for metastasis is unnecessary given the classic symmetric, periarticular appearance and lack of symptoms.

Question 3514

Topic: 10. Pathology and Oncology

A biopsy is taken from a lytic, expansile lesion in the rib of a 20-year-old patient. The histological examination reveals irregular trabeculae of woven bone lacking osteoblastic rimming, set within a bland fibrous stroma. The trabeculae are described as resembling Chinese characters. What is the most likely diagnosis?

. Osteofibrous dysplasia
. Non-ossifying fibroma
. Fibrous dysplasia
. Aneurysmal bone cyst
. Chondromyxoid fibroma

Correct Answer & Explanation

. Fibrous dysplasia

Explanation

Correct Answer: Fibrous dysplasiaThe histological description of irregular woven bone trabeculae resembling Chinese characters or alphabet soup, situated in a bland fibrous stroma without prominent osteoblastic rimming, is the hallmark of Fibrous Dysplasia. This distinguishes it from Osteofibrous Dysplasia (Campanacci disease), which typically occurs in the tibia/fibula of young children and characteristically features prominent osteoblastic rimming around the bone trabeculae.

Question 3515

Topic: Bone Tumors

A 5-year-old boy presents with asymmetric shortening of his right leg and multiple hard, painless swellings on the fingers of his right hand. Radiographs show multiple radiolucent lesions in the metaphyses and diaphyses of the right femur, tibia, and phalanges, with endosteal scalloping. The left side is completely unaffected. What is the most likely diagnosis?

. Multiple epiphyseal dysplasia
. Maffucci syndrome
. Multiple hereditary exostoses
. Ollier disease
. Osteogenesis imperfecta

Correct Answer & Explanation

. Ollier disease

Explanation

Correct Answer: Ollier diseaseOllier disease (multiple enchondromatosis) is a non-hereditary dysplasia characterized by the presence of multiple enchondromas. A classic clinical feature of Ollier disease is its tendency to be highly asymmetric, often predominantly or exclusively affecting one side of the body. The lesions are typically metaphyseal and diaphyseal radiolucencies with endosteal scalloping. Maffucci syndrome would also present with enchondromas but must include soft tissue hemangiomas. Multiple hereditary exostoses presents with osteochondromas (bony outgrowths), not radiolucent enchondromas.

Question 3516

Topic: Bone Tumors
A 9-year-old girl presents with a progressive shepherd's crook deformity of the proximal femur, precocious puberty, and irregular hyperpigmented skin macules with 'coast of Maine' borders. Which of the following is the underlying genetic mutation responsible for this condition?
. GNAS1
. EXT1
. FGFR3
. COMP
. COL1A1

Correct Answer & Explanation

. GNAS1

Explanation

This patient presents with the classic triad of McCune-Albright syndrome: polyostotic fibrous dysplasia (shepherd's crook deformity), endocrine abnormalities (precocious puberty), and café-au-lait spots with irregular borders ('coast of Maine'). Fibrous dysplasia is a condition of anarchic development of bone constituents caused by a somatic activating mutation in the GNAS1 gene, which encodes the alpha subunit of the stimulatory G protein (Gs-alpha). This leads to increased intracellular cAMP, resulting in the proliferation of undifferentiated mesenchymal cells that replace normal marrow with fibrous tissue. EXT1 is associated with multiple hereditary exostoses, FGFR3 with achondroplasia, COMP with pseudoachondroplasia, and COL1A1 with osteogenesis imperfecta.

Question 3517

Topic: 10. Pathology and Oncology

A 25-year-old male with a known history of multiple hereditary exostoses (MHE) presents with a rapidly enlarging, painful mass over his right proximal humerus. Which of the following features on MRI is most indicative of malignant transformation to secondary chondrosarcoma?

. Presence of bone marrow continuity between the lesion and host bone
. Cartilage cap thickness greater than 2 cm
. Pedunculated morphology of the lesion
. Intralesional stippled calcifications
. Location in the appendicular skeleton

Correct Answer & Explanation

. Cartilage cap thickness greater than 2 cm

Explanation

Correct Answer: Cartilage cap thickness greater than 2 cmMultiple hereditary exostoses (osteochondromatosis) is characterized by the anarchic development of cartilage-capped bony outgrowths. The most feared complication is malignant transformation into secondary chondrosarcoma, which occurs in approximately 1-5% of patients with MHE. Clinical signs include new-onset pain or growth of the lesion after skeletal maturity. On MRI, a cartilage cap thickness of greater than 1.5 to 2.0 cm in an adult is highly suspicious for malignant transformation. Bone marrow continuity is a defining feature of all osteochondromas, not a sign of malignancy. Pedunculated morphology and appendicular location are typical of benign lesions, whereas malignant transformation is more common in sessile lesions in the axial skeleton or proximal limb girdles.

Question 3518

Topic: 10. Pathology and Oncology

A 14-year-old boy is diagnosed with multiple enchondromas predominantly affecting the unilateral right hand and lower extremity. Physical examination reveals multiple soft tissue hemangiomas, and radiographs show phleboliths within the soft tissues. What is the most likely diagnosis and its associated risk of malignant transformation compared to isolated multiple enchondromatosis?

. Maffucci syndrome; higher risk of malignant transformation
. Ollier disease; higher risk of malignant transformation
. Maffucci syndrome; lower risk of malignant transformation
. Ollier disease; lower risk of malignant transformation
. Trevor disease; equal risk of malignant transformation

Correct Answer & Explanation

. Maffucci syndrome; higher risk of malignant transformation

Explanation

Correct Answer: Maffucci syndrome; higher risk of malignant transformationThe presence of multiple enchondromas associated with soft tissue hemangiomas (indicated by phleboliths on radiographs) is the hallmark of Maffucci syndrome. Ollier disease involves multiple enchondromas without the vascular anomalies. Both are disorders of anarchic cartilage development. Maffucci syndrome carries a significantly higher risk of malignant transformation (up to 100% in some long-term follow-up studies, including chondrosarcomas and other non-skeletal malignancies like astrocytomas and GI tract malignancies) compared to Ollier disease, which has a malignant transformation rate of approximately 25-30%.

Question 3519

Topic: Bone Tumors

When planning surgical correction for a severe shepherd's crook deformity in a patient with polyostotic fibrous dysplasia, which of the following fixation constructs is most appropriate to minimize the risk of recurrence and implant failure?

. Cortical bone grafting alone
. Load-bearing plate and screw construct
. Intramedullary nailing
. External fixation
. Cancellous bone grafting with K-wires

Correct Answer & Explanation

. Intramedullary nailing

Explanation

Correct Answer: Intramedullary nailingIn fibrous dysplasia, the bone is structurally weak due to the replacement of normal bone with woven bone and fibrous tissue. Surgical management of deformities, such as the shepherd's crook deformity of the proximal femur, requires osteotomies for realignment followed by robust fixation. Intramedullary nailing (a load-sharing device) is the gold standard because it protects the entire length of the bone and bypasses the dysplastic bone, significantly reducing the risk of implant failure and recurrent deformity. Load-bearing devices like plates and screws frequently fail because the screws pull out of the soft dysplastic bone. Bone grafting alone (especially cancellous) is ineffective as the graft is rapidly resorbed and replaced by dysplastic host tissue.

Question 3520

Topic: Bone Tumors

A 10-year-old child with multiple hereditary exostoses presents with a progressive forearm deformity. Radiographs reveal a large sessile osteochondroma of the distal ulna. According to the Masada classification, which of the following is the most common associated deformity pattern in the forearm?

. Radial shortening with ulnar bowing and radial deviation of the carpus
. Ulnar shortening with radial bowing and ulnar deviation of the carpus
. Proximal radioulnar synostosis
. Dorsal subluxation of the distal radioulnar joint without bowing
. Volar dislocation of the radial head

Correct Answer & Explanation

. Ulnar shortening with radial bowing and ulnar deviation of the carpus

Explanation

Correct Answer: Ulnar shortening with radial bowing and ulnar deviation of the carpusIn multiple hereditary exostoses, forearm deformities are common and typically result from osteochondromas affecting the distal ulna (Masada Type I). Because the distal ulna contributes heavily to the longitudinal growth of the ulna, an osteochondroma here retards ulnar growth, leading to ulnar shortening. The radius continues to grow but is tethered to the shortened ulna, resulting in radial bowing. The loss of ulnar support at the wrist leads to an increased distal radial articular angle and subsequent ulnar deviation (ulnar slip) of the carpus. Radial head dislocation can occur in severe cases but is a secondary consequence of the primary ulnar shortening and radial bowing.

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