Topographical Analysis of the Hamate for Proximal Pole Scaphoid Nonunion Reconstruction

Biomechanics of Proximal Hamate Autograft in Scaphoid Nonunion

Purpose  Treatment of proximal scaphoid fractures remains a challenge with a risk of nonunions and avascular necrosis due to its retrograde blood supply. The ipsilateral proximal hamate has been described as a viable autograft option for osteochondral reconstruction of the proximal scaphoid. Our study evaluated the changes in the contact area and pressure of the radioscaphoid joint after proximal hamate autograft reconstruction. Methods  Thin sensors (Tekscan Inc., Boston, MA) were placed in the radiocarpal joints of six fresh-frozen cadaveric forearms. Each specimen's tendons were loaded to 150 N in neutral, 45-degree flexion/extension positions through five cycles. Through a dorsal wrist approach, the proximal 10 mm of the scaphoid and hamate was excised. The proximal hamate autograft was affixed to the scaphoid with K-wires. Peak contact pressures and areas at the scaphoid facet were determined and averaged across loading cycles. Results  At the radioscaphoid facet, peak contact pressures were equivalent, although an increasing trend in the neutral and extended wrist position was seen. At the radiolunate facet, contact pressure had an increasing trend in the hamate reconstructed wrists in all wrist positions. Contact areas had a decreasing trend and were nonequivalent at the radioscaphoid facet in the hamate reconstructed wrist. Conclusion  After hamate autograft, the contact areas were not equivalent between the native and reconstructed wrists but contact pressures were equivalent in the facets. The proximal hamate has a more pointed morphology compared with the proximal scaphoid, which would explain the change in contact area in the hamate autografted wrist. Our study suggests hamate autograft may present a viable reconstruction for the proximal pole of the scaphoid without significantly altering peak contact pressures at the radioscaphoid facet.

Scaphoid and Carpal Bone Fracture: The Difficult Cases and Approach to Management

Scaphoid and carpal bone fractures are challenging injuries to manage and have significant functional implications. Prompt diagnosis is important and relies on systematic evaluation via history, examination, and imaging. Cross-sectional imaging is often helpful for diagnosis and treatment planning. Treatment for nondisplaced fractures is often closed but these injuries typically require prolonged immobilization and may still result in nonunion or avascular necrosis. Displaced carpal bone fractures, and those associated with carpal instability, typically require open reduction internal fixation.

Does Proximal Hamate Graft for Proximal Scaphoid Reconstruction Restore Native Wrist Kinematics?

BACKGROUND

The objective of this study was to determine whether reconstruction of the proximal pole of the scaphoid with a proximal hamate graft restores native carpal kinematics.

METHODS

A cadaveric study was designed assessing wrist kinematic after proximal hamate graft for proximal pole of the scaphoid nonunion. Wireless sensors were mounted to the carpus using a custom pin and suture anchor system to 8 cadavers. A wrist simulator was used to move the wrist through a cyclical motion about the flexion/extension and radial/ulnar deviation axes. Each specimen was tested under a series of 3 conditions: (1) a native state, "Intact"; (2) fractured scaphoid proximal pole, "Fracture"; and (3) post-reconstruction of the proximal pole of the scaphoid using a proximal hamate graft, "Graft."

RESULTS

The fracture condition resulted in a statistically significant change in scapholunate kinematics across the entire arc of motion relative to the intact condition. Reconstruction with proximal hamate grafts restored scapholunate kinematics close to the intact state in both flexion/extension and radial/ulnar deviation axes. The lunocapitate flexion during wrist flexion was significantly different after the hamate graft reconstruction.

CONCLUSIONS

Proximal hamate to scaphoid transfer resulted in restoration of near normal carpal kinematics to the intact state.

Proximal Hamate Reconstruction of Proximal Pole Scaphoid Nonunion: A Case Series and Analysis of Clinical Outcomes

BACKGROUND

Small proximal pole scaphoid nonunions present a clinical challenge influenced by fragment size, vascular compromise, deforming forces exerted through the scapholunate interosseous ligament (SLIL), and potential articular fragmentation. Osteochondral autograft options for proximal pole reconstruction include the medial femoral trochlea, costochondral rib, or proximal hamate. This study reports the clinical outcomes of patients treated with proximal hamate osteochondral autograft reconstruction.

METHODS

A retrospective review identified patients treated with this surgery from 2 institutions with a minimum 6-month follow-up. Clinical outcomes included the Visual Analog Dcale pain score, 12-item Short-Form survey, abbreviated Disabilities of the Arm, Shoulder, and Hand (QuickDASH) score, wrist and forearm range of motion (ROM), radiographic assessment, and complications. We reviewed and compared these outcomes with those of the current published literature.

RESULTS

Four patients (mean age: 24 years, 75% men) with a 12.8-month average follow-up (range: 6-20 months) were included. Radiographic union was identified in all cases by 12 weeks (range, 10-12). The average wrist ROM was 67.5% flexion/extension and 100% pronation/supination compared with the contralateral side at the final follow-up. The mean QuickDASH score was 17.6 (SD, 13). No complications were identified.

CONCLUSIONS

Proximal pole scaphoid nonunion reconstruction using autologous proximal hamate osteochondral graft demonstrated encouraging clinical and radiographic outcomes. Proximal hamate harvest involves minimal donor site morbidity without a distant operative site, uses an osteochondral graft with similar morphology to the proximal scaphoid, requires no microsurgical technique, and permits reconstruction of the SLIL using the volar capitohamate ligament.

Reconstruction of proximal pole scaphoid non-union with avascular necrosis using proximal hamate: A four-case series

Union of proximal pole scaphoid fracture is challenging because the vascular supply is limited. The avascular necrosis accompanying non-union and progressive fragmentation make surgical reconstruction difficult. The present study aimed to report short-term results of reconstruction with proximal hamate in proximal pole scaphoid non-union with avascular necrosis. Four patients (3 male, 1 female) were assessed for non-union following proximal pole scaphoid fracture. Mean age was 25.7 years (range, 22-35 years). Mean interval between injury and reconstruction was 7.5 years (range, 5-9 years). In 3 patients, no treatment was given following the fracture and in the other internal fixation was performed following cast immobilization. The non-united avascular proximal scaphoid was resected and reconstructed with proximal hamate autograft. Mean follow-up was 14.0 months (range, 9-22 months) after reconstruction. At the last control, cases were evaluated in terms of clinical and functional status, and radiologic union was determined on CT scan. Three patients reported subjective decrease in pain. Mean grip strength proportionally to the unaffected side was 24% (range, 8-51%), mean flexion-extension was 55.3% (range, 21-60%), and radial-ulnar deviation was 63.6% (range, 25-100%). Mean QuickDASH score was 32.3 (range, 13.6-52.2). Union was observed in all patients. Proximal hamate reconstruction provided union and pain relief, but only moderate objective functional results. It can be used as an alternative technique in proximal pole scaphoid non-union with avascular necrosis.

A Morphometric Analysis of Hamate Autograft for Proximal Scaphoid Reconstruction

Objective  Recently, authors have investigated using the proximal hamate as osteochondral autograft for proximal pole scaphoid reconstruction in the case of nonunion with avascular necrosis. The aim of our study was to analyze the morphology and anatomic fit of the proximal hamate compared with the proximal pole of the scaphoid using cadaveric specimens. Materials and Methods  Ten cadaver specimens (five males and five females) were dissected. Scaphoid and proximal hamate bones were measured by two independent investigators using electronic calipers and radius of curvature gauges. After measurements were determined to have good correlation, the average value of the two observers' measurements were used for further analysis. Sagittal radius of curvature (ROC), coronal ROC, depth, width, and maximum graft length were compared. Results  The average depth of the scaphoid proximal pole was 12.3 mm (standard deviation [SD] = 1.12) compared with 11.3 mm (SD = 1.24) for the proximal hamate ( p  = 0.36). The average width was 7.8 mm (SD = 1.00) in the scaphoids compared with 8.6 (SD = 1.05) in the hamates ( p  = 0.09). There was also no significant difference in the sagittal ROC between hamates (9.1 mm, SD = 1.13) and scaphoids (9.5 mm, SD = 0.84; p  = 0.36). All of these average measurements were within 1 mm. There was a significant difference between the coronal ROC of the hamate (23.4 mm) and scaphoid (21.1 mm) bones in our samples ( p  = 0.03). Females were on average smaller than their males, but there was no significant difference in fit based on sex alone. Conclusion  The proximal pole of the hamate has similar morphology and size as the scaphoid, with similar depth, width, and sagittal ROC. It has potential as an osteochondral autograft for proximal pole scaphoid reconstruction.

Management of Proximal Pole Scaphoid Nonunions: A Critical Analysis Review

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Optimal management of nonunions of the proximal pole of the scaphoid is controversial and dependent on many patient and pathophysiologic considerations.

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If the proximal pole subchondral bone support is sufficient, options include open reduction and internal fixation, either alone or in combination with autologous nonvascularized or vascularized bone graft.

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If the proximal pole is not salvageable, replacement with osteochondral autografts or osteochondral flaps is the only option for reconstruction of the native anatomy.