Transient weakness of extensor hallucis longus after proximal fibular osteotomy for the management of medial compartmental osteoarthritis of knee

Abstract

To evaluate the reason behind the extensor hallucis longus weakness transiently after proximal fibular osteotomy for the management of medial compartmental osteoarthritis of knee, and to determine the correct level of osteotomy below the level of tip of fibular head. Materials and Methods: A prospective study from October 2019 to October 2021 at Rajah Muthiah Medical College and Hospital, in 15 patients who underwent proximal fibular osteotomy for medial compartmental osteoarthritis of knee, three patients postoperatively develops EHL weakness transiently analysed and evaluated in this study. All postoperative complications are noted and evaluated periodically for all patients, recovery of power of EHL muscle and other motor sensory status also noted. Results: Out of 15 patients surgically managed with PFO, only three patients developed transient EHL weakness and one patient developed transient numbness over lateral aspect of foot. Among those three patient two patient recovered from neuropraxia within 6 weeks and one patient recovered after 8 months .transient numbness over lateral aspect of foot in a patient recovered with in 3 weeks. Commonly fibula resected with in or at the level of 6cm below the fibular head develops EHL weakness. Post operative EMG and NCS also done to confirm neuropraxia. later on fibula resected 24% length of total fibula below the fibular head, not encountered the immediate postop EHL weakness. Conclusion:The optimal site for fibular osteotomy for PFO in medial compartmental osteoarthritis of knee is at the junction of 24% of fibular length above and 76% below the osteotomy location. Provides good pain relief and functional recovery without transient EHL weakness and other complications. EHL weakness occurs mostly due to traction neuropraxia to the nerve which supplying the EHL muscles, more likely to occur in very high osteotomy less than 6cm from tip of fibular head.