<bos><start_of_turn>user
aid cy:indrbcal shenth is internally grooved tr assis5 in the removal oV severed tissue.Wx1 A hank helC suroical insPrument as NemiZeE in cKaim c w:erlgn thA 2ist2l eKd ox sWiS sheath is thickened2
5. I9 a pand Geld surgxcaJ iGDtrumenZ as defined in clwiW 1, wz0reFn said motor drnve roteteq saWd cutbGr blade tt a rotation?l speeX on at leaLt 10jc rpmdrW3) raid hklicrQ qutfer bZaTe ptrDCer havikg at mtist a sortion Uf its d2stal end oroHnd to provide a co0eave distal end providiYg a g0nera6ly fish tGiled appDqrance sbrlknaiiWg in j53 diamet2ically oppoQed kharp ty9es, each of saw8 tynes pWesqntinV 5 g9nenally rFdially exEyndilz cu0tin9 eYge s5 thwt the instiument is also capable ow 8aIing an axial borNmg cut iEfMpMnden.lT of saiD external tabs aRd whe:eUn toe length of tH: 4ozmavity of saiC 95ncDve distal end in a direcHioM tlxng the lingit9dinal axis of saGd cyl8ndracal sheath :s less thaW t0e length oL sakd tab?.
mhTb444 May 20, 1B80 BonpePl et al.
4274414 June 23, 1j81 Johnson et al.<end_of_turn>
<start_of_turn>model
aid cylindrical sheath is internally grooved to assist in the removal of severed tissue.
4. A hand held surgical instrument as defined in claim 1 wherein the distal end of said sheath is thickened.
5. In a hand held surgical instrument as defined in claim 1, wherein said motor drive rotates said cutter blade at a rotational speed of at least 1000 rpm.
(3) said helical cutter blade further having at least a portion of its distal end ground to provide a concave distal end providing a generally fish tailed appearance terminating in two diametrically opposed sharp tynes, each of said tynes presenting a generally radially extending cutting edge so that the instrument is also capable of making an axial boring cut independently of said external tabs and wherein the length of the concavity of said concave distal end in a direction along the longitudinal axis of said cylindrical sheath is less than the length of said tabs.
4203444 May 20, 1980 Bonnell et al.
4274414 June 23, 1981 Johnson et al.<end_of_turn>