Minimally-invasive hallux arthrodesis with endomedullary and a crossed screw fixation

BACKGROUND

Minimally invasive surgery has several advantages: minor pain, smaller incisions and less tissue damage than traditional open surgery. Hallux arthrodesis with an endomedullary screw fixation provides compression and axial stability. The aim of this study was to describe the procedure and evaluate our first results of the minimally invasive first metatarsophalangeal arthrodesis with an endomedullary screw combined with a crossed screw fixation.

METHODS

We retrospectively studied 15feet, with a minimum 1year follow-up. Patients were evaluated with full-load radiographs and AOFAS score preoperatively and at last follow-up.

RESULTS

Consolidation rate was 93.3%, radiological consolidation time was 18 weeks (14-60). Radiographic alignment was achieved with satisfactory results. The preoperative AOFAS score improved from a mean 49 to 90 (p=0.001). There was one postoperative superficial site infection, which healed and a patient developed a pseudarthrosis but it was asymptomatic.

CONCLUSIONS

The minimally invasive metatarsophalangeal arthrodesis with an intramedullary screw is a secure procedure with comparable results to open techniques.

LEVEL OF CLINICAL EVIDENCE

4.

3D digital image correlation evaluation of arthrodesis implants

BACKGROUND

Hallux valgus is a pathological condition that is typically treated via the Lapidus procedure. The purpose of this study was to understand the biomechanical characteristics of bone, implant devices and the bone-implant interface.

METHODS

In-situ digital image correlation was performed on polyurethane foam, a known bone substitute in a modified three-point bend test frame. We introduced this modified rig as an enhanced methodology for characterizing bone and implant device mechanical performance. This new methodology was validated using aluminum rod specimens, in three and four-point bend setups followed by new configurations to reveal implications of load configurations on joint displacement and implant performance. Bone substitute specimens were constructed with nitinol staples or locking plate to minimize gapping at the 1^st tarsometatarsal during testing.

FINDINGS

Bone-implant interface characterization was enabled by digital image correlation, identifying maximum strain concentrations of 1.5% along the interfaces. Interfacial characteristics were analyzed in context with gap displacement allowed by the implant over cyclical loading. The locking plate implant and nitinol staples gapped an average of 2.2 mm and 3.2 mm respectively under 50 Newtons. Removing all load, the locking plate implant and nitinol staples averaged ~0.8 mm and ~0.3 mm of residual gapping respectively.

INTERPRETATION

Our results demonstrate that locking plates provide more initial stability and resistance against gapping under load but are unable to recover compression throughout repetitive loading as seen with the nitinol staple technology. This could lead to a paradigm shift in materials used for early weight bearing protocols post-operation.

The success rate of first metatarsophalangeal joint lateral soft tissue release through a medial transarticular approach: A cadaveric study

BACKGROUND

The objective of this study was to evaluate the success rate of first metatarsophalangeal joint (MTPJ) lateral soft tissue release through a medial transarticular approach.

METHODS

Ten cadaveric specimens were used (6 females/4 males, mean age, 73.4years). Lateral release was performed through a 4cm medial approach using a number 15 blade. Surgical aim was to release four specific structures: lateral capsule, lateral collateral ligament (LCL), adductor hallucis tendon (AHT) and lateral metatarsosesamoid suspensory ligament (LMSL). Once completed, a dissection of the first intermetatarsal space was performed. Success rate was graded in accordance to the number of structures successfully released: 0% (no structures), 25% (1/4), 50% (2/4), 75% (3/4) and 100% (4/4). Inadvertent injuries to other soft tissue structures were recorded.

RESULTS

The success rate for lateral soft tissue release was 100% in 7 cadaveric specimens, and respectively 75%, 50% and 25% in the other 3 specimens. The LCL was successfully released in all specimens. The lateral joint capsule, AHT and LMSL were released in 80% of the specimens. Chondral damage to the first metatarsal head, unintended release of the conjoined tendon and lateral head of the flexor hallucis brevis (FHB) occurred respectively in 40%, 50% and 20% of the specimens.

CONCLUSIONS

Our cadaveric study demonstrated high success rate in the release of specific lateral soft tissue structures of the first MTPJ through a medial transarticular approach. Inadvertent release of the lateral head of the FHB, conjoined tendon and iatrogenic chondral damage of the first metatarsal head are complications to be considered.

LEVEL OF EVIDENCE

Cadaveric study - Level V.

Evaluation of the 1st metatarso-sesamoid joint using standing CT - The Stanmore classification

BACKGROUND

Little is understood about the role that relative sesamoid displacement and chondral wear have on outcome after hallux valgus (HV) surgery. All existing methods to evaluate relative sesamoid displacement have limitations and furthermore, there have been no radiographic studies evaluating metatarso-sesamoid joint wear. Standing CT scan circumvents many of the existing problems in evaluation of relative sesamoid displacement, and also enables the first radiographic study assessing metatarso-sesamoid joint wear.

METHODS

Fifty feet (in 43 patients) with symptomatic HV (Group A) were compared with a control group of 50 feet (50 patients) (Group B). All images were standardised to enable reproducible measurements. The hallux valgus angle, Intermetatarsal angle, sesamoid rotation angle, sesamoid position and metatarso-sesamoid joint space were measured in all patients.

RESULTS

The intra and inter-observer reliability correlation showed that the standing CT assessment of sesamoid position (1.000), rotation (0.991) and metatarso-sesamoid joint space (0.960) were highly reproducible. There was a highly significant difference (p<0.0001) in sesamoid position, sesamoid rotation and metatarso-sesamoid joint space between Group A and Group B.

CONCLUSIONS

Standing CT has been shown to be a reproducible and accurate method of assessing the relative sesamoid displacement and metatarso-sesamoid joint space narrowing. The results have been used to propose a novel standing CT based classification of hallucal sesamoids, considering the degree of displacement and wear. This classification may ultimately facilitate research to provide new insight into the effect relative sesamoid displacement and chondral wear have on outcomes from hallux valgus surgery.

Scarf osteotomy without internal fixation for correction of hallux valgus: A clinical and radiographic review of 148 cases

BACKGROUND

Hallux valgus is a common condition with in excess of 120 procedures described in the literature for its correction. Traditionally, distal metatarsal osteotomies have been employed in the treatment of mild deformities, with proximal osteotomies being reserved for more severe presentations. The Scarf osteotomy without internal fixation allows large translations which can successfully correct severe hallux valgus deformities, without limitations related to screw placement.

METHODS

This is a retrospective single surgeon case series performed over a three year period. One hundred and forty-eight cases were identified, with an average follow up time of 16.5 months. Visual analogue scales were used to obtain preoperative and postoperative pain and cosmetic scores, with the Foot and Ankle Disability Index (FADI) index used to assess functional status. The hallux valgus angle (HVA) and intermetatarsal angle (IMA) were assessed on preoperative and postoperative AP weight-bearing foot X-rays.

RESULTS

The mean pain score improved from 7.04/10 preoperatively to 0.29/10 postoperatively. The mean cosmetic score improved from 2.1/10 to 9.1/10 postoperatively. The mean preoperative HVA and IMA were 35.04° and 15.04°, respectively. The mean postoperative HVA and IMA were 11.54° and 4.83°, respectively. The mean postoperative FADI score was 103.4/104. We report a loss of correction in two cases. One revision surgery was performed.

CONCLUSIONS

We report a large series of cases of the modified Scarf osteotomy as described by Maestro-a versatile, cost-effective, safe and reliable technique with the potential for three dimensional correction. Whilst this is a technically demanding procedure, we recommend the use of the modified Scarf osteotomy in the treatment of a wide range of hallux valgus deformities.

Radiographic evaluation of first MTP joint arthrodesis for severe hallux valgus: Does the introduction of a lag screw improve union rates and correction of the intermetatarsal angle?

BACKGROUND

First metatarsophalangeal (MTP-1) joint fusion is a reliable method for the correction of various deformities including hallux valgus and hallux rigidus. Ideal constructs provide high rates of fusion in desired alignment. The present study examines the union rates, as well as the change in dorsiflexion angle during the follow up period in patients who underwent MTP-1 fusion with a dorsal locking plate and a lag screw, versus patients fused with a dorsal locking plate alone.

METHODS

This is a retrospective review of 99 feet undergoing MTP-1 fusion. Joints were fused using either a dorsal locking plate alone or a lag screw plus a dorsal locking plate. Union was determined radiographically during the follow up period. Suspected nonunions were confirmed with CT. Dorsiflexion angles were radiographically measured at first post-operative visit and at final follow up.

RESULTS

There were 36 patients in the lag screw plus dorsal plate group, and 63 in the dorsal plate group. Mean follow up was 12.9 months (Range: 12-33.5 months). The dorsal plate plus lag screw group had a significantly lower change in mean dorsiflexion angle (0.57°±5.01°) during the post-operative period compared to the dorsal plate group at final follow up versus the dorsal plate group (6.73°±7.07°).

CONCLUSION

The addition of a lag screw to a dorsal locking plate for MTP-1 arthrodesis may offer improved stability of the joint in the sagittal plane over time compared to a dorsal plate alone.

LEVEL OF EVIDENCE

Retrospective level III evidence.

Minimal resection interposition arthroplasty of the first metatarsophalangeal joint

BACKGROUND

Interposition arthroplasty of the first metatarsophalangeal (MTP) joint is a viable alternative to fusion in patients with advanced hallux rigidus. The purpose of this study is to evaluate the midterm results of a modification of the technique.

METHODS

Case series of 18 interposition arthroplasties were performed on 13 female patients with Grade III-IV hallux rigidus. The technique included cheilectomy, bunionectomy when needed, minimal resection of the base of the proximal phalanx and interposition of a fascia lata allograft in the first metatarsophalangeal joint. Mean follow up was nine years (range 75-136 months). Patients were evaluated according to the AOFAS score, the ability to tip toe and their subjective satisfaction.

RESULTS

There was a significant difference between preoperative (mean 43.2, range 15-83) and postoperative (mean 77.3, range 40-100) AOFAS scores (p<0.001). The patients were able to tip toe on 12 of the 18 operated feet and 9 of the 13 patients were satisfied from the operation. All dissatisfied patients had a coexistent hallux valgus deformity.

CONCLUSIONS

The technique had satisfactory midterm outcomes in older patients with advanced hallux rigidus without hallux valgus. Advantages of the method are the preservation of tip toe function in most patients and a technically easy conversion to fusion when needed.