A further increase in the number of total hip arthroplasty (THA) is predicted, in particular the number of young THA patients has raised and with it their demands. There is no standardized evidence-based rehabilitation program and no reliable guidelines for sports activities after THA. Stretching and strengthening gymnastics are routinely performed in rehabilitation and aerobics as a sport after THA. The aim of the investigation was to determine the in vivo force and moments acting on the hip prosthesis during gymnastics and aerobic exercises to provide a source for evidence-based recommendations. Hip joint loads were measured in six patients with instrumented hip implants. The resulting force FRes, bending moment MBend at the neck and torsional moment MTors at the stem were examined during seven strengthening (with two different resistance bands) and four stretching gymnastic exercises and seven aerobic exercises with and without an aerobic step board compared to the loads during the reference activity walking. The stretching and strengthening gymnastics exercises and the aerobic exercises with and without a board demonstrated in their median peak force and moments mostly lower or similar values compared to walking. Significantly increased loads were recorded for the flexor stretching exercise in monopod stand (Fres and MBend), the strengthening abduction exercise on the chair (MTors) and the strengthening flexion exercise with the stronger resistance band (MTors). We also found a significant increase in median peak values in aerobic exercises with a board for the "Basic Step" (ipsilateral started Fres and MTors; contralateral started MTors), "Kickstep ipsilateral started" (Fres and MTors) and "Over the Top contralateral started" (Fres). The in vivo loads in THA patients during frequently performed stretching, strengthening and aerobic exercises were demonstrated for the first time. It was proved that stretching gymnastic exercises are safe in terms of resulting force, bending and torque moments for THA patients, although an external assistance for stabilization may be considered. Strengthening gymnastics exercises are reliable in terms of Fres, MBend and MTors, but, based on our data, we recommend to adhere to the communicated specific postoperative restrictions and select the resistance bands with lower tension. Aerobic exercises without an aerobic board can be considered as reliable activity in terms of force and moments for THA patients. Aerobic exercises with a board are not recommended for the early postoperative period and in our opinion need to be adapted to the individual muscular and coordinative resources.

Hip joint loads need careful consideration during postoperative physiotherapy after joint replacement. One factor influencing joint loads is the choice of footwear, but it remains unclear which footwear is favorable. The objective of the present study was to investigate the influence of footwear on hip joint loads in vivo. Instrumented hip endoprostheses were used for in vivo load measurements. The parameters resultant contact force (Fres), bending moment (Mbend) and torsional moment (Mtors) were evaluated during treadmill walking at 4 km/h with different shoe types. In general, footwear tended to increase hip joint loading, with the barefoot shoe having the least influence. Fres and Mbend were significantly increased during heel strike for all shoe types in comparison to barefoot walking, with everyday shoe (34.6%; p = 0.028 and 47%; p = 0.028, respectively) and men’s shoe (33.2%; p = 0.043 and 41.1%; p = 0.043, respectively) resulting in the highest changes. Mtors at AbsMax was increased by all shoes except for the barefoot shoe, with the highest changes for men’s shoe (+ 17.6%, p = 0.043) and the shoe with stiffened sole (+ 17.5%, p = 0.08). Shoes, especially those with stiff soles or elaborate cuishing and guiding elements, increase hip joint loads during walking. The influence on peak loads is higher for Mtors than for Fres and Mbend. For patients in which a reduction of hip joints loads is desired, e.g. during physiotherapy after recent surgery or to alleviate symptoms of osteoarthritis, low profile shoes with a flexible sole may be preferred over shoes with a stiff sole or elaborate cushioning elements.

Objective To evaluate the influence of Nordic walking (NW) on hip joint loads in order to determine whether it can be safely performed during postoperative physiotherapy in patients after orthopeadic surgery of the hip. Methods Internal hip joint loads were directly measured in vivo in 6 patients using instrumented hip prostheses during NW and ordinary walking (OW). All patients received training in two different NW techniques (double-poling and the diagonal technique) by a certified NW instructor. Measurements were conducted on a treadmill at a speed of 4 km/h on level ground, at 10% inclination and at 10% slope as well as on a level lawn at a self chosen comfortable speed. Resultant contact force (Fres), bending moment (Mbend) and torsional torque (Mtors) were compared between NW and OW as well as between both NW techniques. Results Joint loads showed a double peak pattern during all setups. Neither NW technique significantly influenced hip joint loads at the time of the first load peak during contralateral toe-off (CTO), which was also the absolute load peak, in comparison to OW. Compared to OW, double-poling significantly reduced Fres and Mbend at the time of the second load peak during the contralateral heel strike (CHS) on level ground both on the treadmill (− 6% and − 7%, respectively) and on the lawn (− 7% and − 9%). At 10% inclination, the diagonal technique increased Fres and Mbend at CHS (by + 6% and + 7%), but did not increase the absolute load peak at CTO. Conclusion Joint loads during NW are comparable to those of OW. Therefore, NW can be considered a low-impact activity and seems to be safe for patients that are allowed full weight bearing, e.g. during postoperative rehabilitation after THA.

ZusammenfassungDer menschliche Gang als Methode der Fortbewegung ist eines der individuellsten Charakteristika eines jeden Menschen. Die ersten Durchführungen einer Ganganalyse waren visuell und wurden durch den jeweiligen Arzt durchgeführt, um frühzeitig klinische Entscheidungen bei Gangdysfunktionen treffen zu können. Mit der Entwicklung neuer Technologien und der Verwendung von kinetischen Belastungsplatten sowie der Kombination mit der elektromyografischen Untersuchung kam es zu rapiden Fortschritten bei der Analyse des menschlichen Ganges. Der Gangzyklus wird aufgeteilt in eine Stand- und eine Schwungphase, die jeweils 60 – 65% bzw. 35 – 40% des Gangzyklus ausmachen. Diese 2 Phasen werden in weitere Untereinheiten aufgegliedert. Es erfolgen Messungen bezüglich der temporalen Aspekte wie z. B. Geschwindigkeit, Zeit-Distanz-Parameter sowie der räumlichen Parameter, z. B. Schrittlänge des Ganges. Die Anwendung neuester Methoden wie z. B. die 3-D-Analyse des Gangzyklus in Kombination mit der Elektromyografie und der Anwendung von Kraftmessplatten spielen bei orthopädisch-unfallchirurgischen Patienten eine bedeutende Rolle. Die Limitierung dieser Messungen durch die Ortsgebundenheit und die mangelnde Flexibilität der Platten wird durch die Verwendung von Laufbändern mit integrierten Druck- und Kraftmessplatten überwunden. Neueste Entwicklungen moderner Belastungssohlen erleichtern durch die alltägliche Praktikabilität die Anwendung der Ganganalyse bei Alltagsaktivitäten. In Kombination mit der WLAN-Technik erschließen sich durch die schnelle Datenübertragung neue zukunftsweisende Anwendungsfelder. Die benutzerfreundliche Anwendung der Belastungssohlen wird zukünftig im Hochleistungssport, in der Prothesenanpassung, der Planung von Amputationen, bei der Evaluierung neuropädiatrischer Erkrankungen und sogar der forensischen Medizin breite Anwendung finden.