I knew Mom shouldn't have had a hip replacement but she insisted (mostly because the other people in her assisted living facility have one). Now she has even more trouble walking because a nerve in her lower leg got pinched or stretched (they are not sure which). What causes this to happen?
Studies in this area agree that about half the time, it is unclear what the true cause of the problem may be. Clearly, the nerve gets pinched, pressed, cut, deprived of oxygen, or exposed to high heat and sometimes the cause is a combination of those factors. The result can be muscle weakness, loss of normal motor function (movement), and altered sensation.
When the lower leg is affected, it is usually because the peroneal nerve (a branch of the much larger sciatic nerve) has been damaged. The large sciatic nerve splits just above the knee to form the tibial nerve and the common peroneal nerve. These two nerves travel to the lower leg and foot, supplying sensation and muscle control. The tibial nerve continues down the back of the leg while the common peroneal nerve travels around the outside of the knee and down the front of the leg to the foot. Both of these nerves can be damaged by injuries around the knee.
This is a rare complication. According to a recent study from Thomas Jefferson University Hospital in Philadelphia, Pennsylvania one-third of one percent (0.32%) of their patients (that's 31 out of 9,570) had a confirmed case of peroneal nerve palsy following a total hip replacement.
By taking a look at all the patient characteristics of the 31 patients and comparing them to the rest of the (much larger) group, the authors were able to see one risk factor predicting peroneal nerve palsy. Younger age (less than 56 years old) increased the risk of nerve palsy and poor or slow recovery.
They also saw one prognostic factor (i.e., able to predict when peroneal nerve palsy is more likely to happen). Being significantly overweight (obese) influences recovery in a negative way. In other words, a larger body-mass index (BMI) is a red flag for potential nerve problems associated with total hip replacement.
Even with CT scans and MRIs, the exact cause of the peroneal palsy was not known in half of the 31 cases. Some of the reasons why patients did develop this type of nerve palsy included compression from a hematoma (pocket of blood), lipoma (benign fat tumor), and screw used in the hip replacement (pressing against the nerve).
There were quite a few cases from traction (pulling) on the nerve either directly or indirectly from the use of a surgical tool known as a retractor. In a smaller number of patients, hip dislocation or limb lengthening contributed to nerve damage leading to nerve palsy. And one patient developed nerve palsy from being in a position that put pressure on the lower leg bone (fibula), which in turn, pressed against the nerve.
Jai Hyung Park, MD, PhD, et al. Common Peroneal Nerve Palsy Following Total Hip Arthroplasty: Prognostic Factors for Recovery. May 2013. Vol. 95A. No. 9. Pp. e55(1)-e55(5).
*Disclaimer:* The information contained herein is compiled from a variety of sources. It may not be complete or timely. It does not cover all diseases, physical conditions, ailments or treatments. The information should NOT be used in place of visit with your healthcare provider, nor should you disregard the advice of your health care provider because of any information you read in this topic.